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DOI： 10.1002/cplu.201900087

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-VCH Verlag  

We have established a convenient method for the base-promoted direct amination of β-unsubstituted 5,15-diazaporphyrins (DAPs) with secondary and primary amines to produce 3,7,13,17-tetraamino- and 3-amino-DAPs, respectively, regioselectively. The amino groups attached at the periphery cause significant red shifts of the absorption bands as a result of their perturbation of the HOMO and/or LUMO in the DAP π-system. The palladium complex of a 3,7,13,17-tetrakis(diphenylamino)-DAP generated singlet oxygen in high yield under irradiation with near-infrared light.

DOI： 10.1002/anie.201800471

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In spite of significant advances in redox-active porphyrin-based materials and catalysts, little attention has been paid to 20 pi and 19 pi porphyrins because of their instability in air. Here we report the meso-modification of 5,10,15,20-tetraarylporphyrin with two nitrogen atoms, which led to redox-switchable 20 pi, 19 pi, and 18 pi 5,10,15,20-tetraaryl-5,15-diazaporphyrinoids (TADAPs). Three kinds of metal(II) complexes and free bases of TADAP were prepared by the metal-templated annulation of the corresponding metal-bis(dipyrrin) complexes. The inductive and resonance effects of the meso-nitrogen atoms on the aromatic, optical, electrochemical, and magnetic properties of the entire TADAP pi-systems were assessed by using various spectroscopic measurements and density functional theory calculations. The aromaticity and pi-pi* electronic transition energies of the TADAPs varied considerably, and were shown to be dependent on the oxidation states of the pi-systems. In contrast to the isoelectronic 5,10,15,20-tetraarylporphyrin derivatives, the 20 pi and 19 pi TADAPs were chemically stable under air. In particular, the 19 pi TADAP radical cations were extremely stable towards dioxygen, moisture, and silica gel. This reflected the low-lying singly occupied molecular orbitals of their pi-systems and the efficient delocalization of their unshared electron spin. The capability of MgTADAP to catalyze aerobic biaryl formation from aryl Grignard reagents was demonstrated, which presumably involved a 19 pi/20 pi redox cycle.

DOI： 10.1002/chem.201703664

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The first examples of air-stable 20-electron 5,10,15,20-tetraaryl-5,15-diaza-5,15-dihydroporphyrins, their 18-electron dications, and the 19-electron radical cation were prepared through metal-templated annulation of nickel(II) bis(5-arylamino-3-chloro-8-mesityldipyrrin) complexes followed by oxidation. The neutral 20-electron derivatives are antiaromatic and the cationic 18-electron derivatives are aromatic in terms of the magnetic criterion of aromaticity. The meso Natoms in these diazaporphyrinoids give rise to characteristic redox and optical properties for the compounds that are not typical of isoelectronic 5,10,15,20-tetraarylporphyrins.

DOI： 10.1002/anie.201510734

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Phosphole is a chemically tunable heterole, and its pi-conjugated derivatives are potential candidates for optoelectronic materials. This account describes recent developments in the synthesis and structure-property relationships of pi-conjugated phosphole derivatives made by my research group. Thiophene-phosphole-styrene, phosphole-acetylene-arene, oligophosphole, polyphosphole, areno[c]phosphole, and phosphole-heterole pi systems are synthesized using titanacycle-mediated metathesis and palladium-catalyzed cross-coupling reactions. The structural, optical, and electrochemical properties of selected compounds are discussed. Initial results on some applications of thiophene-phosphole copolymers, acenaphtho[c]phospholes, and amin-terthiophene-phosphole donor-pi-acceptor dyes in organic solar cells are described. These results give valuable information and guidelines for designing new phosphorus-containing organic materials for molecular electronics.

DOI： 10.1002/tcr.201402101

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Society of Synthetic Organic Chemistry, Japan  

Phosphole has a low aromaticity and exhibits characteristic optical and electrochemical properties derived from the phosphorus-bridged 1,3-diene π system. In addition, phosphole has an active lone pair at phosphorus. The most remarkable feature of the phosphole-based π-systems is that their fundamental properties are tunable by chemical functionalizations at the phosphorus center. In this regard, phosphole-based π-systems are now regarded as one of the future materials for use in optoelectronics. In this article, we would like to briefly summarize our recent results on the synthesis of novel π-conjugated phosphole derivatives with representative examples, which contain phosphole-vinylene, phosphole-acetylene, phosphole-heterole, phosphole-benzene, phosphole-phosphole, benzo[c]phosphole, acenaphtho[c]phoshole, and diacenaphtho[b,d]phosphole skeletons. The target compounds were successfully prepared by two main approaches, titanacycle method and Stille coupling. Selected structural, optical, and electrochemical data for a few derivatives are also presented. The results described herein would give valuable information and guidelines for designing phosphole-based opto-electrochemical materials.

DOI： 10.5059/yukigoseikyokaishi.70.629

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<jats:title>Abstract</jats:title>
<jats:p>We report herein an improved method for the quantitative preparation of free bases of 5,10,15,20-tetraaryl-5,15-diazaporphyrinoid (TADAP) using Me3SiBr–MeOH to treat the corresponding zinc(II) complexes. Metallation of the free base with HSiCl3 followed by Si–X metathesis with SbF3 and redox reactions afforded difluorosilicon(IV) complexes of TADAP.</jats:p>

DOI： 10.1093/bulcsj/uoad022

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Recently reported highly fluorescent 2-phenylbenzo[b]phospholium salt shows an interesting photochemical property. While the counter anion and solvent dependency indicate that the salt is mainly responsible for the absorption and fluorescence spectra, the fluorescence decay clearly depends on the counter anion. In the present study, the detailed mechanism is elucidated using quantum chemical computation and its hybrid with statistical mechanics called 3D-RISM-SCF. Based on the careful exploration of plausible structures of the ion pairs in the methanol and dichloromethane solution, we identify the structure of the charge transfer state, the key on the photoprocess.

DOI： 10.1016/j.molliq.2023.121934

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Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/bcsj.20230071

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：World Scientific Pub Co Pte Ltd  

<jats:p> Singlet–singlet and triplet-triplet energy-transfer processes between anthracenes and porphyrins have received considerable attention in materials chemistry. Herein, we report the first examples of 3,5-bis(10-phenylanthracen-9-yl)benzene-appended porphyrins (BPABPs) designed to study intramolecular energy transfer between two chromophores. The Curtius rearrangement of 3,5-bis(10-phenylanthracen-9-yl)benzoyl azide in the presence of the platinum(II) complex of 5,10,15-tris(3,5-di-tert-butylphenyl)-20-(3-hydroxyphenyl)porphyrin or its free base in toluene afforded the corresponding BPABP. Spectroscopy, cyclic voltammetry, and density functional theory calculations revealed that the anthracene and porphyrin [Formula: see text]-electron systems of the BPABPs are not conjugated and consequently do not affect each other’s absorption properties. In contrast, the BPABPs exhibited considerably different luminescence properties to those of phenyl 3,5-bis(10-phenylanthracen-9-yl)carbamate and 5,10,15-tris(3,5-di-tert-butylphenyl)-20-(3-methoxyphenyl)porphyrins; the anthracene units of the BPABPs show considerably quenched fluorescence compared to that of the reference anthracene, indicative of efficient intramolecular singlet–singlet energy transfer from the anthracene to the porphyrin unit. The phosphorescence quantum yield of the Pt complex of BPABP is comparable to that of the reference Pt-porphyrin, which suggests that intramolecular triplet-triplet energy transfer from the Pt-porphyrin to the anthracene unit is inefficient. The present findings improve our understanding of how structural factors and excited-state energy levels affect energy transfer and triplet-triplet annihilation upconversion processes of covalently linked bisanthracene-appended porphyrins. </jats:p>

DOI： 10.1142/s1088424623500840

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1,2,5,10-Tetraphenylanthra[2,3-b]phosphole oxides and 1-methyl-1,2,5,10-tetraphenylanthra[2,3-b]phospholium salts were prepared, and their optical properties were investigated. The substituent at the para position and the fused anthracene moiety were found to exert significant impacts on the fluorescence properties of the P-bridged 2-styrylanthracene skeleton.

DOI： 10.1021/acs.joc.2c01107

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The synthesis, excited state dynamics, and substituent effect on the 1O2-generation efficiency of several copper(II) complexes of 5,15-diazaporphyrin (CuDAPs) bearing peripheral substituents are reported. 10,20-Diaryl-CuDAPs were prepared via a new method consisting of metal-templated cyclization and N-dealkylation as key steps. The effect of the β-substituents on the optical and redox properties of CuDAP was stronger than that of the meso-aryl groups, which can be explained by considering the characteristics of the HOMO and LUMO of the DAP ring. The excited state dynamics and 1O2-generation efficiency of CuDAPs were studied using time-resolved spectroscopic techniques; the electronic effect of the meso-aryl groups on the triplet lifetime and 1O2-generation quantum yield was relatively weak, whereas that of the β-(1-pyrazolyl) groups was appreciable. The analysis of the temperature dependence of phosphorescence spectra of 10,20-bis(2,4,6-trimethylphenyl)-CuDAP allowed the energy gap between the excited trip-quartet and trip-doublet states to be determined. The relatively long triplet lifetimes of CuDAPs show their potential for future application as photosensitizers.

DOI： 10.1246/bcsj.20220002

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Porphyrins containing hydrophilic auxiliaries have received considerable attention. Herein we report the first examples of strongly hydrophilic copper(II) complexes of 5,10,15,20-tetraaryl-5,15-diazaporphyrins (TADAPs) substituted with carboxy or (2,3-dihydroxypropyl)carbamoyl groups. Metal-templated cyclization reactions of a common dipyrrin precursor with nickel(II) or copper(II) acetate afforded the corresponding metal(II) complexes of 5,10,15,20-tetrakis(4-alkoxycarbonylphenyl)-5,15-diazaporphyrin (M-TADAP-COOR; M = Ni, Cu) as air-stable 19[Formula: see text] radical cations, which were reversibly interconvertible with 20[Formula: see text]- and 18[Formula: see text]-electron states by redox reactions. NMR spectroscopy of 20[Formula: see text] and 18[Formula: see text] Ni-TADAP-COORs revealed antiaromatic and aromatic characteristics, respectively. Alkaline hydrolysis of the 19[Formula: see text] Cu-TADAP-COOR afforded a carboxylic acid, Cu-TADAP-COOH, which was freely soluble in water under basic conditions, but poorly soluble under neutral or acidic conditions. Dehydrative condensation of Cu-TADAP-COOH with 2,3-bis((tert-butyldimethylsilyl)oxy)propan-1-amine followed by deprotection of the silyl groups afforded an amide, Cu-TADAP-CONHR, with four (2,3-dihydroxypropyl)carbamoyl groups. Although the 20[Formula: see text] Cu-TADAP-CONHR was poorly soluble in water, oxidation of its DAP ring notably changed the solubility, and the resulting 18[Formula: see text] dication was homogeneously dispersed in neutral water. Cyclic voltammetry of the present TADAP derivatives showed the 21[Formula: see text]/20[Formula: see text], 20[Formula: see text]/19[Formula: see text] and 19[Formula: see text]/18[Formula: see text] redox couples in the range of −1.8 to +0.2 V vs. Fc/Fc[Formula: see text]. Furthermore, Cu-TADAP-CONHR exhibited reversible redox processes in neutral water. This study shows that TADAP could be a potential platform for the development of hydrophilic DAP-based materials.

DOI： 10.1142/s1088424621500917

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/cl.210218

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcb.1c02360

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We report on the synthesis and optical, magnetic, and electrochemical properties of nickel(II) and copper(II) complexes of 5,10,15,20-tetraaryl-5,15-diazaporphyrin–tertiary amine (TADAP–TA) conjugates. Metal-templated cyclization reactions of 9-(4-(dimethylamino)phenyl)amino-1-chloro-5-mesityldipyrrin and 9-(4-(diphenylamino)phenyl)amino-1-chloro-5-mesityldipyrrin (mesityl = 2,4,6-trimethylphenyl) with nickel(II) or copper(II) acetate afforded the corresponding metal(II) complexes of TADAP–TA. The 20[Formula: see text], 19[Formula: see text], and 18[Formula: see text] oxidation states of the DAP ring in the TADAP – TAs were reversibly interconvertible by redox reactions. NMR spectroscopy of the 20[Formula: see text] and 18[Formula: see text] Ni-TADAP – TAs revealed their antiaromatic and aromatic characters, respectively, whereas electron paramagnetic resonance spectroscopy of the 19[Formula: see text] Ni-TADAP–TAs showed effective delocalization of an unshared electron spin in the DAP ring. The interconversion between the three oxidation states of TADAP – TAs also caused a distinct change in the optical properties of the DAP [Formula: see text]-electron system. Notably, all the 18[Formula: see text] dications exhibited weak and broad absorption bands in the near infrared region owing to the charge-transfer from the peripheral tertiary amine units (donor) to the cationic DAP center (acceptor). Cyclic voltammetry of TADAP – TAs exhibited the reversible 20[Formula: see text]/19[Formula: see text] and 19[Formula: see text]/18[Formula: see text] redox couples and the irreversible amine oxidation at the periphery. The electrochemical oxidation of the Ni-TADAP–triphenylamine conjugate generated reactive ammoniumyl radicals, which underwent intermolecular coupling to form a polymer of TADAP–TA on the electrode surface.

DOI： 10.1142/s1088424619500822

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Nickel(II) and copper(II) complexes of redox-switchable 20 pi, 19 pi, and 18 pi 5,15-dialkyl-10,20-diaryl-5,15-diazaporphyrins were prepared through a metal-templated cyclization method. Furthermore, the terminal silyloxy groups in the peripheral N-alkyl chains were transformed into hydroxy groups by deprotection. It is worth noting that redox reactions between the 19 pi and 18 pi systems bearing hydroxy groups caused a change in the water solubility of the diazaporphyrin chromophore.

DOI： 10.1002/ajoc.201900085

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The synthesis, aromaticity, and optical and electrochemical properties of zinc(II) complexes of 10,15,20-triaryl-15-aza-5-oxaporphyrin (TriAAOP) were investigated. Metal-templated cyclization of a zinc(II) 1,19-dichloro-5,10,15-triaryl-10-azatetrapyrrin complex with an oxygen source afforded 20 pi TriAAOP in the neutral form. Oxidation of 20 pi TriAAOP with silver (I) hexafluorophosphate generated the 19 pi radical cation or 18 pi dication depending on the content of oxidant used. The interconversion between the three oxidation states (18 pi, 19 pi, and 20 pi) resulted in distinct changes in the aromaticity and optical properties of the 15-aza-5-oxaporphyrin pi-system. Nuclear magnetic resonance spectroscopy of 20 pi TriAAOP revealed its antiaromatic character, whereas that of the 18 pi TriAAOP dication showed its aromatic character. The combined effect of the two meso-heteroatoms was directly reflected in the redox properties of the porphyrin ring; TriAAOP was reduced more easily and more difficult to oxidize than the zinc(II) complex of 5,10,15,20-tetraaryl-5,15-diaz-aporphyrin (TADAP). In the ultraviolet-visible-near-infrared spectra of the materials, the lowest-energy electronic excitations of the 19 pi and 18 pi TriAAOP derivatives were considerably red-shifted compared with those of the isoelectronic TADAP derivatives. Based on the results of density functional theory calculations, it was concluded that the observed differences between TriAAOP and TADAP would arise from the high electronegativity of oxygen; specific frontier orbitals of the TriAAOP pi-systems were energetically stabilized relative to those of the TADAP pi-system. The present findings corroborate that the meso-modification of a porphyrin rings with different kinds of heteroatoms is a promising strategy to fine tune their light-response properties that are switchable by reversible single electron transfer processes.

DOI： 10.1002/hc.21456

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Aromatic substitution reactions were applied to the divergent synthesis of a series of symmetrically and unsymmetrically 3,5-disubstituted BODIPYs bearing N-heteroaryl groups. Furthermore, the effect of N-heteroaryl substituents at the 3- and 5-positions on the optical and photophysical properties of the BODIPY π-electron system was elucidated.

DOI： 10.1021/acs.joc.8b00087

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We have synthesized dithieno[3,4-b:3′,4′-d]phosphole derivatives as a new type of thiophene-fused phospholes. These dithienophospholes were found to show intramolecular charge transfer interactions by introducing electron-donating or -withdrawing groups on the peripheral aryl groups. Namely, they exhibit the unique hybrid character of electron-withdrawing phosphole and electron-donating thiophene.

DOI： 10.1021/acs.joc.8b00030

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/acs.joc.8b00030

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

We have established a convenient method for the base-promoted direct amination of β-unsubstituted 5,15-diazaporphyrins (DAPs) with secondary and primary amines to produce 3,7,13,17-tetraamino- and 3-amino-DAPs, respectively, regioselectively. The amino groups attached at the periphery cause significant red shifts of the absorption bands as a result of their perturbation of the HOMO and/or LUMO in the DAP π-system. The palladium complex of a 3,7,13,17-tetrakis(diphenylamino)-DAP generated singlet oxygen in high yield under irradiation with near-infrared light.

DOI： 10.1002/ange.201800471

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The β-functionalization of 5, 15-diazaporphyrins (DAPs) with phosphoryl, phenoxy, sulfanyl, and sulfonyl groups was achieved by either cross-coupling or aromatic nucleophilic substitution reactions of β-bromo- and β, β′-dibromo-DAPs. The heteroatom-containing functional groups at the β- positions strongly affected the redox properties of the DAP π-systems.

DOI： 10.1246/bcsj.20180123

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The synthesis and optical, electrochemical, and magnetic properties of nickel(II) complexes of 5,10,20-triaryl-5,15-diazaporphyrin (TriADAP) are reported. Metal-templated cyclization of unsymmetrically substituted nickel(II)-bis(1-amino-9-chloro-5-mesityldipyrrin; mesityl = 2,4,6-trimethylphenyl) complexes afforded the corresponding TriADAPs or 5-aryl-15-benzyl-10,20-dimesityl-5,15-diazaporphyrin, depending on the combination of base and solvent. The latter macrocycle was converted to TriADAP by deprotection of the N-benzyl group through Pd/C-promoted hydrogenation. TriADAPs were isolated in both 18 pi (cation) and 19 pi (neutral) forms. The interconversion between these two oxidation states resulted in a distinct change in the optical properties of the DAP pi-system. NMR spectroscopy of the 18 pi TriADAP cations showed that they had aromatic character, whereas EPR spectroscopy of the 19 pi TriADAP showed a highly delocalized electron spin of the pi-radical. The para substituents of the N-aryl groups of TriADAPs had a small but distinct impact on their HOMO and LUMO energies. The change in the net charge of one electron was directly reflected in the redox properties of the DAP ring; TriADAP was more easily reduced and less easily oxidized than DAP. The difference in the net charge was also reflected by the shielding of the pyrrolic beta-protons observed in the H-1 NMR spectra. The present results confirm that TriADAP is a highly promising framework for constructing a new class of azaporphyrin-based materials with 18 pi-19 pi redox-switchable optical and magnetic properties.

DOI： 10.1142/S1088424618500529

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Various 7-substituted benzo[b]phosphole derivatives were prepared by PO-directed lithiation of 1,2,3-triphenylbenzo[b]phosphole P-oxide and subsequent iodination and cross-coupling reactions. The electron-donating groups introduced at the 7-position produced dramatic solvatofluorochromism owing to the strong charge-transfer character of the excited state of the entire π-system.

DOI： 10.1039/c8dt01503a

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DOI： 10.1021/jacs.7b09424

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In this work, we investigated the effects of counter anions, P-substituents, and solvents on the optical and photophysical properties of 2-phenylbenzo[b]phospholium salts in solution. A series of 2-phenylbenzo[b] phospholium salts was prepared by P-alkylation or P-phenylation of 1,2-diphenylbenzo[b]phosphole followed by anion exchange reactions. X-ray crystallographic analyses of six benzo[b] phospholium salts showed that each phosphorus center has an onium nature with an essentially tetrahedral geometry. H-1 NMR and steady-state UV-vis absorption and fluorescence spectroscopic measurements of these phospholium salts revealed the pivotal role of counter-anion solvation. The observed results are discussed on the basis of the association-dissociation equilibrium between a contact ion pair (CIP) and a solvent-separated ion pair (SSIP) in solution. The hexafluorophosphates exist as SSIPs and emit intense fluorescence, irrespective of the P-substituents and solvents. In contrast, the iodides are present as SSIPs in methanol but exist as equilibrium mixtures of the two emitting species, SSIP and CIP, in dichloromethane. As a consequence, fluorescence intensities of the iodides varied significantly depending on the solvents, P-substituents, and solution concentrations. These findings were studied in more detail using time-resolved fluorescence spectroscopy and fluorescence titration measurements. The light-emitting properties of the 2-phenylbenzo[b] phospholium halides in the CIPs rely on heavy atom effects derived from the counter halide anions on the S-1 state of the adjacent cationic benzo[b] phosphole pi-systems. The present study suggests that 2-arylbenzo[b] phospholium salts would be promising scaffolds for developing new phosphole-based ionic fluorophores that are capable of responding to external stimuli such as anionic species and solvents.

DOI： 10.1039/c7dt01839h

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Liquid crystalline donor (i.e., phthalocyanine) was covalently linked to acceptor (i.e, fullerene) to achieve efficient charge-transport properties in a liquid crystalline phase. The columnar structure exhibited highly efficient ambipolar charge-transport character, demonstrating the potential utility of the strategy in organic electronics. © 2011 American Chemical Society.

DOI： 10.1021/ja203822q

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Excited-state proton transfer (ESPT) of 5-cyano-2-naphthol (5CN2) and 5,8-dicyano-2-naphthol (DCN2) in three different protic ionic liquids (PILs), triethylammonium trifluoromethanesulfonate ([N222H][CF3SO3]), triethylammonium methanesulfonate ([N222H][CH3SO3]), and triethylammonium trifluoroacetate ([N222H][CF3COO]), was studied by time-resolved fluorescence. In [N222H][CF3SO3], both 5CN2 and DCN2 showed fluorescence only from ROH∗ (normal form of substituted naphthol in the excited states), indicating that no ESPT occurred in [N222H][CF3SO3]. For 5CN2 in [N222H][CH3SO3], fluorescence bands from ROH∗ and RO-∗ (anionic form of substituted naphthol in the excited states) were observed, indicating that 5CN2 could dissociate proton to surrounding solvents and form RO-∗. More interestingly, 5CN2 in [N222H][CF3COO] and DCN2 in [N222H][CH3SO3] and [N222H][CF3COO] showed an anomalous fluorescence band around 470 nm (5CN2) or around 520 nm (DCN2) which has not been reported previously. The kinetics of each fluorescent component of 5CN2 and DCN2 was analyzed on the basis of the time profile of fluorescence intensity. Plausible ESPT schemes of 5CN2 and DCN2 were discussed on the basis of the kinetics and the basicity of anion in PILs. (Graph Presented).

DOI： 10.1021/acs.jpcb.7b03658

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The first examples of unsymmetrical -substituted donor--acceptor (D--A)-type 5,15-diazaporphyrin (DAP) sensitizers with both p-aminophenyl and p-carboxyphenyl groups at their peripheral 3-, 7-, 13-, and/or 17-positions have been synthesized for use in dye-sensitized solar cells (DSSCs). UV/Vis absorption and emission spectroscopy, electrochemical measurements, and DFT calculations revealed that these D--A dyes exhibit high light-harvesting properties over the whole visible range because of the intrinsic charge-transfer character of their electronic transitions. The cell performances of TiO2-based DSSCs fabricated with the newly prepared DAP derivatives were evaluated under standard AM1.5 conditions. Among the four dyes examined, 13,17-bis(p-carboxyphenyl)-3,7-bis[p-(N,N-dimethylamino)phenyl]-DAP showed the highest power conversion efficiency (2.0%), which was 20times larger than that obtained with 3-(p-carboxyphenyl)-DAP. These results show that the DAP chromophore could be used as the electron-accepting unit in various types of functional dyes.

DOI： 10.1002/cplu.201700051

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NH-bridged and pyrazine-fused metallodiazaporphyrin dimers have been prepared from nickel(II) and copper(II) complexes of 3-amino-5,15-diazaporphyrin by Pd-catalyzed C-N cross-coupling and oxidative dimerization reactions, respectively. The synergistic effects of the nitrogen bridges and meso-nitrogen atoms play major roles in enhancing the light-harvesting properties and delocalization of an electron spin over the entire pi-skeletons of the metallodiazaporphyrin dimers.

DOI： 10.1002/asia.201700204

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One-pot treatment of dibenzothiophene dioxides with phenylphosphine and KOH in DMSO at ambient temperature provides the corresponding dibenzophosphole oxides after oxidative workup. Substitution of the endocyclic SO2 unit with PPh could proceed via an intermolecular SNAr reaction of the dioxides with potassium phenylphosphide followed by another SNAr reaction in an intramolecular fashion. Various dibenzophospholes have been synthesized from readily available dibenzothiophene dioxides and were investigated from a photophysical viewpoint.

DOI： 10.1002/ajoc.201600612

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Chemical modification at the periphery with nitrogen or chalcogens is a highly promising strategy to diversify the optical, electrochemical, magnetic, and coordination properties of the porphyrin family. Indeed, various kinds of phthalocyanines and related benzo-annelated azaporphyrinoids have been synthesized, and their fundamental properties have been extensively investigated. However, the synthesis of heteroatom-containing porphyrins in which the peripheral methine groups are partially replaced with nitrogen or chalcogens remains a considerable challenge. In this review, we will focus mainly on recent advances in the synthesis of aza-, oxa-, and thiaorphyrins and related compounds, including historically important examples.

DOI： 10.1021/acs.chemrev.6b00460

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The base-induced Sommelet-Hauser (S-H) rearrangement of azetidine-2-carboxylic acid ester-derived ammonium salts into 2-aryl-substituted derivatives was demonstrated. The ring-strain of four-membered N-heterocycles enables efficient generation of the desired ylide intermediate and enhances the rate of the S-H rearrangement. The asymmetric version of the rearrangement was characterized by excellent levels of successive chirality transmissions. The regio- and stereo-controlled nucleophilic ring opening of the rearrangement products produced quaternary -aryl amino acid esters with excellent enantiopurities.

DOI： 10.1002/ejoc.201600611

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

© 2016 The Royal Society of Chemistry. The optical, electrochemical, and photophysical properties of Mes2B- (Mes = 2,4,6-trimethylphenyl), Ph2P-, or Ph2MeP+-substituted 2,5-dithienylphospholes and 2-phenyl-5-thienylphospholes are reported. The Mes2B- and Ph2P-substituted derivatives were prepared via regioselective lithiation and metathesis at the thiophene rings of the corresponding unsubstituted π-systems. The Ph2MeP+-substituted derivatives (phosphonium salts) were obtained via methylation of the Ph2P-substituted π-systems. The optical and electrochemical data and density functional theory calculations showed that the highest occupied molecular orbital and lowest unoccupied molecular orbital energies of these α,α′-linked thiophene-phosphole π-systems were sensitive to the intrinsic nature of the B and P substituents. The fluorescence quantum yields (Φf) of the Ph2MeP+-substituted derivatives varied considerably depending on the counter anion, concentration, and solvent, but the π-π∗ transition energies were unchanged. The emitting ability of the Ph2MeP+-substituted 2,5-dithienylphosphole π-system changed significantly from Φf= 0.07 to 0.87. These findings were investigated using time-resolved fluorescence spectroscopy and fluorescence titration measurements. The results show that phosphonium iodides were present in the equilibrium mixtures of three or two emitting ion pairs in CH2Cl2. The light-emitting abilities of the Ph2MeP+-substituted derivatives rely on heavy atom effects derived from the counter halide anions.

DOI： 10.1039/c5dt03362d

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Two diazaporphyrin (DAP)-porphyrin hetero dimers, in β-meso and β-β configurations, were prepared to study their photoinduced intramolecular electron transfer properties. The two meso nitrogen atoms in the porphyrin ring of DAP change its redox potential, making DAP more easily reduced, compared to its porphyrin counterpart. A charge-transfer from porphyrin to DAP in both hetero dimers was verified by versatile optical spectroscopic methods. The steady-state fluorescence spectra indicated an efficient intramolecular exciplex formation for both dimers. For the β-meso dimer, ultrafast time-resolved spectroscopic methods revealed the subpicosecond formation of two types of primary short-living (1-18 ps) intramolecular exciplexes, which relaxed in toluene to form a long-living final exciplex (1.4 ns) followed by a longer-living charge transfer complex (&gt
5 ns). However, in benzonitrile, the lifetime of the final exciplex was longer (660 ps) as was that of the charge transfer complex (180 ps). The β-β analogue formed similar short-living exciplexes in both solvents, but the final exciplex and the charge transfer state had significantly shorter lifetimes. The electrochemical redox potential measurements and density functional theory calculations supported the proposed mechanism.

DOI： 10.1021/jp510903a

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© 2015 American Chemical Society. Suzuki-Miyaura cross-coupling reactions were used in the divergent synthesis of a series of 2-arylnaphtho[2,3-b]phosphole P-oxides and their benzo[b]phosphole counterparts. We elucidated the electronic and steric effects of the 2-aryl groups and fused arene moieties on the optical and photophysical properties of these two types of phosphole-based π-systems.

DOI： 10.1021/acs.joc.5b00541

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The syntheses and optical/electrochemical properties of 3-aryl-10,20-dimesityl-5,15-diazaporphyrin-metal complexes (MDAPs; mesityl = 2,4,6-trimethylphenyl; M = Ni, Zn) are reported. Treatment of 3-bromo-MDAPs with arylboronic acids in the presence of a Pd catalyst and a bulky phosphine ligand in a dioxane-water mixed solvent afforded the corresponding 3-aryl-MDAPs in moderate to good yields. X-ray crystallographic analysis of p-EtO2CC6H4-NiDAP showed that the beta-aryl group was tilted toward the NiDAP ring, with a dihedral angle of 21.7 degrees. In the UV-visible absorption spectra, all the Ar-MDAPs showed intense Q-bands attributable to HOMO-to-LUMO transitions. The para substituents were found to influence the HOMO energies, which eventually resulted in fine tuning of the HOMO-LUMO gaps of the diazaporphyrin chromophores. It is worth noting that the p-Ph2NC6H4-ZnDAP showed broad absorption and emission bands in the visible-near-infrared regions. The large Stokes shifts and their linear solvation energy relationships vs. orientation polarizability show that this Ph2N-substituted derivative has intrinsically high charge transfer from the triphenylamine (donor) to the ZnDAP (acceptor) unit. These experimental observations were supported by theoretical calculations for model Ar-ZnDAP compounds. These results confirm that the introduction of a highly electron-donating aryl group at the peripheral beta-carbon is a promising strategy for enhancing the light-harvesting and light-emitting abilities of diazaporphyrin-based pi-systems in the visible-near-infrared regions.

DOI： 10.1142/S1088424615500509

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The first examples of pyrrole- and thiophenebridged 5,15-diazaporphyrin (DAP) dimers are prepared through Stille coupling reactions of nickel(II) and copper(II) complexes of 3-bromo-10,20-dimesityl-5,15-diazaporphyrin (mesityl = 2,4,6-trimethylphenyl) with the respective 2,5-bis-(tributylstannyl)heteroles. The effects of the heterole spacers and meso nitrogen atoms on the optical, electrochemical, and magnetic properties of the DAP dimers are investigated by UV/Vis absorption spectroscopy, density functional theory calculations, magnetic circular dichroism spectroscopy, cyclic voltammetry, and EPR spectroscopy. The heterole spacers are found to have a significant impact on the electronic transitions over the entire p-system. In particular, the pyrrolebridged DAP dimers exhibit high light-harvesting potential in the low-energy visible/near-infrared region owing to the intrinsic charge-transfer character of the lowest excitation.

DOI： 10.1002/chem.201405482

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-Blackwell  

New donor-π-acceptor organic (D-π-A) dyes composed of triarylamine, oligothiophene, and phosphole subunits were prepared, and their optical and photovoltaic properties were investigated. The regioselective α-lithiation of the thiophene ring of 2-(thiophen-2-yl)phospholes bearing an ester group, followed by treatment with tributyltin chloride afforded 2-(5-(tributylstannyl)thiophen-2-yl)phosphole derivatives, which underwent Stille coupling with 5′-(p-(diarylamino)phenyl)-5-bromo-2,2′-bithiophene to give triarylamine-terthiophene-phosphole hybrid π systems bearing the terminal ester group. The alkaline hydrolysis of the ester group yielded the target dyes, bearing the carboxylic acid anchoring group. The UV-vis absorption spectra of the new N,S,P-hybrid dyes displayed broad and intense π-π∗ transitions with two absorptionmaxima in the visible region. Density functional theory (DFT) calculations of two dye models revealed that each highest occupied molecular orbital (HOMO) resides on the triarylamine-oligothiophene π network, whereas each lowest unoccupied molecular orbital (LUMO) is basically located on the phosphole subunit. In addition, the time-dependent DFT calculations of the models showed that the lowest energy bands of these hybrid dyes are mainly consisted of the HOMO-to-LUMO+1 and HOMO-to-LUMO transitions with the large intramolecular charge-transfer character. The N,S,P-hybrid-dye-sensitized TiO2 cells exhibitedmoderate power conversion efficiencies of up to 5.6%. The present findings corroborate the potential utility of the phosphole skeletons as the acceptor components in the D-π-A sensitizers.

DOI： 10.1002/hc.21188

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Two kinds of phosphole- and benzodithiophene-based copolymers bearing PV=O or PV=NSO2C8H17 functions were prepared by Pd-CuI-promoted Stille coupling reactions, and their optical and electrochemical properties were investigated. Bulk heterojunction organic photovoltaic devices comprised of the new P,S-bridged copolymers and (6,6)-phenyl-C71-butyric acid methyl ester (PC71BM) exhibited power conversion efficiencies of up to 0.65-% under AM1.5 irradiation at 100 mW-cm-2. Copyright © 2014 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

DOI： 10.1002/ejic.201301132

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The first examples of - directly linked, acetylene-bridged, and butadiyne-bridged 5,15-diazaporphyrin dimers have been prepared by palladium-catalyzed coupling reactions of nickel(II) and copper(II) complexes of 3-bromo-10,20-dimesityl-5,15-diazaporphyrin (mesityl=2,4,6-trimethylphenyl). The effects of the linking modes and meso-nitrogen atoms on the structural, optical, electrochemical, and magnetic properties of the distributed systems were investigated by using X-ray crystallography, UV/Vis absorption spectroscopy, DFT calculations, cyclic voltammetry, and ESR spectroscopy. Both the electronic and steric effects of the meso-nitrogen atoms play an important role in the highly coplanar geometry of the directly linked dimers. The direct - linkage produces enhanced conjugation and electron-spin coupling between the two diazaporphyrin units.

DOI： 10.1002/chem.201304626

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Diazaporphyrin-C-60 linked dyad has been prepared to assess intrinsic electron transfer properties of diazaporphyrins for the first time. The dyad exhibited the efficient formation of a charge-separated state which has a lifetime 4x longer than that of the corresponding porphyrin-C-60 linked dyad with the same spacer. In accordance with this elongation, a SnO2 nanostructured electrode modified with the diazaporphyrin-C-60 dyad also revealed enhanced photocurrent generation in the visible region in comparison with that with the porphyrin-C-60 dyad. These results show that diazaporphyrins are highly promising building blocks for the construction of artificial photosynthesis and solar energy conversion.

DOI： 10.1021/jp410436f

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Heck, Stille, and Sonogashira reactions of 2-bromobenzo[b]phosphole P-oxide afforded a series of 2-alkenyl- and 2-alkynyl-benzo[b]phosphole P-oxides. The charge-transfer character of the new benzo[b]phosphole pi-systems in the excited state is enhanced by the terminal electron-donating substituents. Furthermore, the C-Sn cross-coupling of the bromide was applied to the facile synthesis of a new Stille-coupling precursor, 2-stannylbenzo[b]phosphole.

DOI： 10.1021/ol401994e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Carboxyphenylethynyl-substituted diazaporphyrin has been synthesized to assess the utility of diazaporphyrins in dye-sensitized solar cells for the first time. The diazaporphyrin-sensitized TiO₂ cell exhibited photocurrent generation in the visible region of 400–700 nm together with a power conversion efficiency of 0.08%.

DOI： 10.1246/cl.130212

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A new class of polyphospholes bearing alkanesulfonylimino moieties on the phosphorus(V) centers was prepared by the Pd-Cul-promoted Stille coupling reaction to investigate the charge-carrier transport properties of the pi-networks of polyphospholes. Time-of-flight measurements have revealed that the poly(phosphole P-imide)s possess ambipolar charge-carrier mobilities of up to mu(electron) = 6 x 10(-3) cm(2) V-1 s(-1) and mu(hole) = 4 x 10(-3) cm(2) V-1 s(-1).

DOI： 10.1021/ol4000982

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The first comprehensive study of the synthesis and structureproperty relationships of 2,2'-bis(benzo[b]phosphole)s and 2,2'-benzo[b]phospholebenzo[b]heterole hybrid p systems is reported. 2-Bromobenzo[b]phosphole P-oxide underwent copper-assisted homocoupling (Ullmann coupling) and palladium-catalyzed cross-coupling (Stille coupling) to give new classes of benzo[b]phosphole derivatives. The benzo[b]phospholebenzo[b]thiophene and -indole derivatives were further converted to P,X-bridged terphenylenes (X=S, N) by a palladium-catalyzed oxidative cycloaddition reaction with 4-octyne through the C beta H activation. X-ray analyses of three compounds showed that the benzo[b]phosphole-benzo[b]heterole derivatives have coplanar p planes as a result of the effective conjugation through inter-ring C?C bonds. The pp* transition energies and redox potentials of the cis and trans isomers of bis(benzo[b]phosphole) P-oxide are very close to each other, suggesting that their optical and electrochemical properties are little affected by the relative stereochemistry at the two phosphorus atoms. The optical properties of the benzo[b]phospholebenzo[b]heterole hybrids are highly dependent on the benzo[b]heterole subunits. Steady-state UV/Vis absorption/fluorescence spectroscopy, fluorescence lifetime measurements, and theoretical calculations of the non-fused and acetylene-fused benzo[b]phospholebenzo[b]heterole p systems revealed that their emissive excited states consist of two different conformers in rapid equilibrium.

DOI： 10.1002/chem.201203047

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The synthesis, structures, optical and electrochemical properties, and aromaticity of a series of 5,15-diaza-10,20-dimesitylporphyrins (M-DAP; M = Pb, H-2, Ni, Pd, Pt, Zn; mesityl = 2,4,6-trimethylphenyl) are reported. Treatment of mesityl-substituted bis(5,5'-dibromodipyrrin) with sodium azide in the presence of lead(II) acetylacetonate afforded Pb-DAP, which was quantitatively converted to H-2-DAP by acidolysis. The free base H-2-DAP reacted with palladium(II), platinum(II), and zinc(II) salts to give Pd-DAP, Pt-DAP, and Zn-DAP, respectively. The crystal structures, optical and electrochemical properties, and aromaticities of these beta-unsubstituted M-DAPs were comprehensively investigated by X-ray crystallography, UV-vis absorption/fluorescence spectroscopy, nanosecond flash photolysis, cyclic and differential pulse voltammetry, NMR spectroscopy, and density functional theory calculations. The obtained data show that replacement of the 5- and 15-methine carbons with nitrogen atoms alters the intrinsic properties of the porphyrin 18 pi system as follows: (i) the coordination spheres at the N-4 core become contracted while keeping high planarity; (ii) the Q bands are red shifted and largely intensified; (iii) the electron-accepting ability is enhanced, whereas the electron-donating ability is reduced; (iv) the radiative decay rates from the S-1 state are enhanced; and (v) the aromaticity of the 18 pi circuit is slightly reduced in terms of both geometric and magnetic criteria. These optical and electrochemical properties of M-DAPs stem from their characteristic frontier orbitals; two HOMOs and two LUMOs are nondegenerate as a result of the incorporation of the electronegative nitrogen atoms at the two meso positions. In addition, the group 10 metals incorporated at the core finely tune the fundamental properties of DAP pi systems through inductive effects as well as d pi-p pi antibonding orbital interactions; the HOMO-LUMO gaps of the group 10 metal complexes increase in the order Ni-DAP &lt; Pd-DAP &lt; Pt-DAP.

DOI： 10.1021/ic301835c

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A divergent method for the synthesis of a,a'-diarylacenaphtho[1,2-c]phosphole P-oxides has been established; a,a-dibromoacenaphtho[c]phosphole P-oxide, which was prepared through a TiII-mediated cyclization of 1,8-bis(trimethylsilylethynyl)naphthalene, underwent a Stille coupling with three different kinds of aryltributylstannanes to afford the a,a'-diarylacenaphtho[c]phosphole P-oxides in moderate to good yields. X-ray crystallographic analyses and UV/Vis absorption/fluorescence measurements have revealed that the degree of p-conjugation, the packing motif, the electron-accepting ability, and the thermal stability of the acenaphtho[c]phosphole p-systems are finely tunable with the a-aryl substituents. All the P?O and P?S derivatives exhibited high stability in their electrochemically reduced state. To use this class of arene-fused phosphole p-systems as n-type semiconducting materials, we evaluated device performances of the bulk heterojunction organic photovoltaics (OPV) that consist of poly(3-hexylthiophene), an indene-C70 bisadduct, and a cathode buffer layer. The insertion of the diarylacenaphtho[c]phosphole P-oxides as the buffer layer was found to improve the power conversion efficiency of the polymer-based OPV devices.

DOI： 10.1002/asia.201200492

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Society of Synthetic Organic Chemistry, Japan  

Phosphole has a low aromaticity and exhibits characteristic optical and electrochemical properties derived from the phosphorus-bridged 1,3-diene π system. In addition, phosphole has an active lone pair at phosphorus. The most remarkable feature of the phosphole-based π-systems is that their fundamental properties are tunable by chemical functionalizations at the phosphorus center. In this regard, phosphole-based π-systems are now regarded as one of the future materials for use in optoelectronics. In this article, we would like to briefly summarize our recent results on the synthesis of novel π-conjugated phosphole derivatives with representative examples, which contain phosphole-vinylene, phosphole-acetylene, phosphole-heterole, phosphole-benzene, phosphole-phosphole, benzo[c]phosphole, acenaphtho[c]phoshole, and diacenaphtho[b,d]phosphole skeletons. The target compounds were successfully prepared by two main approaches, titanacycle method and Stille coupling. Selected structural, optical, and electrochemical data for a few derivatives are also presented. The results described herein would give valuable information and guidelines for designing phosphole-based opto-electrochemical materials.

DOI： 10.5059/yukigoseikyokaishi.70.629

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The present paper reports the first comprehensive study on the synthesis, structures, optical and electrochemical properties, and peripheral functionalizations of nickel(II) and copper(II) complexes of beta-unsubstituted 5,15-diazaporphyrins (M-DAP; M=Ni, Cu) and pyridazine-fused diazacorrinoids (Ni-DACX; X=N, O). These two classes of compounds were constructed starting from mesityldipyrromethane by a metaltemplate method. Ni-DAP and Cu-DAP were prepared in high yields by the reaction of the respective metalbis(dibromodipyrrin) complexes with NaN3CuX (X=I, Br), whereas Ni-DACN and Ni-DACO were formed as predominant products by the reaction with NaN3. In both cases, the metal centers change their geometry from tetrahedral to square planar during the aza-annulation; X-ray crystallographic analyses of M-DAPs showed highly planar diazaporphyrin p planes. The Q band of Ni-DAP was redshifted and intensified compared with that of a nickelporphyrin reference, due to the involvement of electronegative nitrogen atoms at the meso positions. It was found that the peripheral bromination of Ni-DAP and Ni-DACO occurred regioselectively to afford Ni-DAP-Br4 and Ni-DACO-Br, respectively. These brominated derivatives underwent Stille reactions with tributyl(phenyl)stannane to give the corresponding phenylated derivatives, Ni-DAP-Ph4 and Ni-DACO-Ph. On the basis of the absorption spectra and X-ray analysis, it has been concluded that the attached phenyl groups efficiently conjugate with the diazaporphyrin p system. The present results unambiguously corroborate that the beta-unsubstituted DAPs and DACXs are promising platforms for the development of a new class of p-conjugated azaporphyrin-based materials.

DOI： 10.1002/chem.201200463

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DOI： 10.1002/chem.201103843

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5-(Diphenylphosphanyl)-10,15,20-triarylporphyrins (meso-phosphanylporphyrins) underwent complex. ations with palladium(II) and platinum(II) salts to afford phosphapalladacycle- and phosphaplatinacycle-fused coplanar porphyrin dimers, respectively, via regioselective peripheral beta-C-H activation of the meso-phosphanylporphyrin ligands. The optical and electrochemical properties of these metal-linked porphyrin dimers as well as their porphyrin monomer/dimer references were investigated by means of steady-state UV-vis absorption/fluorescence spectroscopy, cyclic and differential pulse voltammetry, time-resolved spectroscopy (fluorescence and transient absorption lifetimes and spectra), and magnetic circular dichroism spectroscopy. All the observed data clearly show that the palladium(II) and platinum(II) linkers play crucial roles in the electronic communication between two porphyrin chromophores at the one-electron oxidized state and in the singlet-triplet intersystem-crossing process at the excited state. It has also been revealed that the C-Pt-C linkage makes more significant impacts on these fundamental properties than the C-Pd-C linkage. Furthermore, density functional theory calculations on the metal-linked porphyrin dimers have suggested that the antibonding d pi-p pi orbital interaction between the peripherally attached metal and adjacent pyrrolic beta-carbon atoms destabilizes the highest occupied molecular orbitals of the porphyrin pi-systems and accounts for the observed unique absorption properties. On the basis of these experimental and theoretical results, it can be concluded that the linear carbon-metal-carbon linkages weakly but definitely perturb the optical, photophysical, and electrochemical properties of the phosphametallacycle-linked coplanar porphyrin dimers.

DOI： 10.1021/ja210205v

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DOI： 10.1021/jp208775x

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Organic transformations using organobismuth(V) reagents developed by my group are reviewed. The characteristic properties of bismuth, such as the inert pair effect, small bond dissociation energy, and polarized bonding are strongly related to the reactivity of pentavalent organobismuth compounds. The Bi(V) reagents discussed in this chapter include tetraorganylbismuthonium salts ([Ar3RBi+][X-]), triarylbismuth ylides (Ar3Bi=CHCOR), triarylbismuth imides (Ar3Bi=NCOR), triarylbismuth oxides (Ar3Bi=O), and triarylbismuth dichlorides (Ar3BiCl2). These organobismuth(V) compounds are readily accessible in a few steps from triarylbismuthanes (Ar3Bi). New and efficient carbon-carbon bond forming reactions, carbon-heteroatom bond forming reactions, alcohol oxidation, and photoinduced cationic polymerization have been investigated using these reagents. In all these reactions, the good leaving ability as well as the high nucleofugality of the triarylbismuthonio group plays a crucial role in bond-forming and bond-breaking steps.

DOI： 10.1007/128_2011_167

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The synthesis and the catalytic activity of bis(mu-chloro)-bridged, phosphapalladacyclefused diporphyrins (M-porphyrin-appended phosphapalladacycles: M = Zn, Ni, free-base), as well as the coordinating ability of their precursors, meso-phosphanylporphyrins are reported. Treatment of meso-phosphanylporphyrinatozinc(II) with an equimolar amount of PdCl(2)(NCPh)(2) caused regioselective beta-C-H activation of the porphyrin ring to produce bis(mu-chloro)-bridged Zn-porphyrin-appended phosphapalladacycle, which was further converted to the free-base-and Ni-porphyrin-appended analogs. The UV-vis absorption spectra of these palladium complexes showed weak exciton coupling between two porphyrin chromophores connected by the mu-chloro bridges. The M-porphyrinappended phosphapalladacycles behaved as precatalysts for a high temperature Heck reaction between p-bromobenzaldehyde and butyl acrylate. In a range of the catalyst-loading of 0.05-0.005 mol.%, the catalytic activity was found to significantly depend on the central metal incorporated at the porphyrin core. The Ni-porphyrin-appended phosphapalladacycle showed considerably higher turnover frequency than did the Zn-porphyrin-and free-base-porphyrin-appended counterparts. This trend in the catalytic activity does not simply correlate with the sigma-donating ability of the phosphorus center and the electron-donating ability of the porphyrin pi-systems. Instead, it is related to the durability of the precatalysts under the reaction conditions employed. The observed results corroborate that the central metal of the meso-phosphanylporphyrin ligands plays a crucial role in the active Pd(0) catalyst-loading from the porphyrin-appended phosphapalladacycles at constant efficiency.

DOI： 10.1142/S1088424611004087

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Divergent synthesis of 2,5-diarylphosphole derivatives was achieved by using two kinds of Pd-catalyzed cross-coupling reactions. In addition, para- and P-substituent effects on the optical and redox properties of the benzene-phosphole-benzene pi-systems were disclosed experimentally.

DOI： 10.1246/cl.2011.919

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We have prepared a novel push-pull porphyrin with an electron-donating diarylamino group at the meso-position and an electron-withdrawing 4-carboxy-2,3,5,6-tetrafluorophenylethynyl anchoring group at the opposite meso-position to address the substitution effects of the electron-withdrawing fluorine atoms on photovoltaic properties for the first time. The fluoro-substituted porphyrin showed slightly improved light-harvesting properties when compared to the reference porphyrin in solution, due to the enhancement of charge-trapsfer character. The fluoro-substituted porphyrin-sensitized TiO2 cell exhibited a moderate power conversion efficiency of 4.6% but was lower than the corresponding Value (6.9%) of the reference porphyrin-sensitized TiO2 cell. The carboxylic group in the reference porphyrin binds to the TiO2 surface with bidentate coordination, leading to formation of the densely packed monolayer on the TiO2 surface, whereas both of the electron-withdrawing fluorine atoms and the carboxylic group of the fluoro-substituted porphyrin interact with the TiO2 surface, adopting relatively parallel orientation to the TiO2 surface with monodentate binding of the carboxylic acid to the TiO2, eventually yielding to the small surface coverage and low cell performance due to the fast charge recombination and small amount of the long-lived porphyrin radical cation. Such fundamental information may be useful for the molecular design of highly efficient dye-sensitized solar cells based on push-pull porphyrins.

DOI： 10.1021/jp2030208

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DOI： 10.1021/ja203822q

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DOI： 10.1246/bcsj.20100326

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

5,10,15,20-Tetrakis(2,4,6-trimethylphenyl)-6'-carboxylquinoxalino[2,3-b]quinoxalino[12,13-b']porphyrinatozinc(II) (ZnPBQ) is synthesized to evaluate the effects of p elongation of quinoxaline-fused porphyrins on the optical, electrochemical, and photovoltaic properties. ZnPBQ showed an intensified Soret band as well as red-shifted Soret and Q bands relative to 5,10,15,20-tetrakis(2,4,6-trimethylphenyl)-6'-carboxylquinoxalino[2,3-b] porphyrinatozinc(II) (ZnPQ), demonstrating the improved light-harvesting property of ZnPBQ. The optical and electrochemical HOMO-LUMO gaps were consistent with those estimated by DFT calculations. The photovoltaic properties were compared under optimized conditions, in which a sealed device structure with TiCl4-treated, TiO2 double layers was used. The ZnPBQ cell exhibited a relatively high power conversion efficiency (eta) of 4.7 %, which was smaller than that of the ZnPQ cell (eta = 6.3 %). The weaker electronic coupling between the LUMO of ZnPBQ and conduction band (CB) of TiO2 or more tilted geometry of ZnPBQ on the TiO2 surface may result in the low electron injection/charge collection efficiency as well as the low incident photon-to-current efficiency (IPCE) for the ZnPBQ cell (maximum IPCE = 56%) relative to the ZnPQ cell (maximum IPCE = 75 %), leading to the lower eta value of the ZnPBQ cell than that of the ZnPQ cell. In addition, the open-circuit potential of the ZnPBQ cell also slightly decreased with the effect of charge recombination from the electrons injected into the CB of TiO2 to I-3(-).

DOI： 10.1002/cssc.201100029

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

DOI： 10.1002/anie.201007065

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

DOI： 10.1016/j.jcis.2011.01.066

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Language：English   Publisher：American Institute of Physics  

DOI： 10.1063/1.3565237

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

2,5-Bis(1,5-diphenylphosphol-2-yl)heterole derivatives were prepared via Pd-catalyzed Stille-type cross-coupling reactions of alpha-(tributylstannyl) phosphole or alpha-iodophosphole with the corresponding 2,5-difunctionalized heteroles (pyrrole, furan, and thiophene). X-ray crystallographic analyses of three sigma(4)-P derivatives have elucidated that the coplanar phosphole-heterole-phosphole pi-networks are constructed in both anti-anti and anti-anti conformations. In the case of the pyrrole-linked (sigma(4)-P derivatives, there is a weak hydrogen-bonding interaction between NH and P=X (X = O, S) groups. The optical and electrochemical properties of the sigma(3)-P and sigma(4)-P=O derivatives were revealed experimentally by means of UV-vis absorption/emission spectroscopy and cyclic/differential pulse voltammetry. In all the heterole-linked derivatives, the P-oxidation lowers LUMO levels more efficiently than HOMO levels and, as a result, narrows HOMO-LUMO gaps. In each series (sigma(3)-P or sigma(4)-P=O), the lowest pi-pi* transition energies of the phosphole-heterole-phosphole pi-systems were found to decrease in the following order: thiophene &gt; furan &gt; pyrrole, and their electrochemical oxidation and reduction potentials shift to the negative side in the same order. These results basically reflect the differences in ionization potential and electron affinity of the central heterole spacers. Density functional theory calculations on the model compounds supported the experimentally observed results. The HOMO of the molecule resides on the conjugated polyene network of the pi-system, whereas the LUMO is strongly located on the phosphole subunits. The present comparative study demonstrates, for the first time, that the intriguing electronic structures and the fundamental properties of the 2,5-bis (1,5-diphenylphosphol-2-yl)heteroles can be finely tuned by simple selection of the appropriate heterole spacer. (C) 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:457-470, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20708

DOI： 10.1002/hc.20708

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DOI： 10.1002/anie.201102782

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c0ee00482k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

DOI： 10.1039/c1jm11531f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp911141s

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

2,5-Bis(pyrrol-2-yl)phosphole derivatives were prepared using the reaction of titanacycles, generated in situ from a Ti-II reagent and pyrrole-capped 1,6-heptadiynes, with dichloro(phenyl)phosphine. The 2,5-bis(pyrrol-2-yl)phosphole derivatives were found to possess narrower optical HOMO-LUMO gaps and less positive oxidation potentials than those of previously reported 2,5-diarylphosphole analogs. This demonstrates that the intrinsic nature of the electron excessive pyrrole subunits as well as the effective pi-conjugation over the coplanar heterole rings. The sigma(3)-P type 2,5-bis(5-phenylpyrrol-2-yl)phosphole underwent complexation with AuCl(SMe2) and PtCl2 to yield the respective AuCl-monophosphine and PtCl2-bisphosphine complexes. In the square planar Pt-II complex, the pyrrolic NH protons were found to form intramolecular hydrogen bonds with the chlorine atoms that gave rise to symmetrically split, parallel pi-chromophores linked by two Pt-P bonds. Density functional theory calculations on a Pt-II model complex suggested that this cooperative interaction induces a significant split of the original LUMOs of the symmetrical pi-conjugated ligands. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

DOI： 10.1016/j.crci.2010.03.017

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp1004049

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Palladium-copper-promoted Stille-type cross-coupling reactions between alpha-stannylphospholes and alpha-iodophospholes afforded alpha,alpha&apos;-linked oligophospholes and polyphosphole efficiently. It has been revealed that the polyphosphole P-oxide possesses an extremely narrow band gap and a high electron-accepting ability as compared to polythiophene.

DOI： 10.1021/ol100926q

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp102486b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

DOI： 10.1246/cl.2010.448

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/adma.200903056

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

(Figure Presented) P,X,N2-type phosphaporphyrins and phosphacalixphyrins (X = N, S) bearing a perfluorophenyl (C6F 5) group at the core phosphorus atom were prepared In high overall yield from 1-perfluorophenyl-2,5-di(ethoxycarbonyl)phosphole as a common starting material. In addition, P-C6F5 P,S 2,N2-type sapphyrin was successfully prepared as the first example of ring-expanded phosphorus-containing porphyrin. © 2010 American Chemical Society.

DOI： 10.1021/ol100114j

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WALTER DE GRUYTER GMBH  

Our recent studies on the synthesis, structures, and aromaticity of phosphole-containing porphyrins and their metal complexes are summarized. Core-modified P,X,N-2-porphyrins (X = S, N) are accessible from a sigma(4)-phosphatripyrrane and the corresponding 2,5-difunctionalized heteroles in a few steps. X-ray structural analysis of the sigma(3)-P,N-3 porphyrin revealed that it possesses a slightly distorted 18 pi plane. The phosphorus atom incorporated at the core plays an important role in producing unprecedented reactivity and coordinating ability for the porphyrin ring. The P,N-3 free base reacts with [RhCl(CO)(2)](2) in dichloromethane, ultimately yielding an 18 pi P,N-3-rhodium(III) complex, whereas the P,S,N-2 free base undergoes redox-coupled complexation with zero valent group 10 metals to afford the corresponding P,S,N-2-isophlorin-metal(II) complexes. The aromaticity of the free-base porphyrins and the metal complexes was uncovered based on both experimental and theoretical results. It is of particular interest that the P,S,N-2-isophlorin-metal complexes exhibit only a weak antiaromaticity in terms of the magnetic criterion.

DOI： 10.1351/PAC-CON-09-08-05

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp910832a

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(Chemical Equation Presented) The synthesis, structures, optical and redox properties, and reactivity of phosphaporphyrins are reported. The 21-phosphaporphyrin (P,N3-porphyrin) and 23-phospha-21-thiaporphyrin (P,S, N2-porphyrin) were prepared via acid-promoted dehydrative condensation between a phosphatripyrrane and the corresponding 2,5-bis[hydroxy(phenyl)methyl]heteroles followed by 2,3-dichloro-5,6- dicyanobenzoquinone oxidation. Experimental (NMR, UV-vis, and X-ray analyses) and theoretical (DFT calculations) results suggest that the 18π aromaticity inherent in regular N4-porphyrins was maintained in these phosphaporphyrins. X-ray crystallography revealed a slightly distorted 18π aromatic ring for the P,N3-porphyrin with the phosphole and three pyrrole rings tilted from the 24-atoms mean plane by 9.6° and 3.8-15.4°, respectively. DFT calculations on model compounds showed that the P,X,N2-porphyrins (X = N, S) possess considerably small HOMO-LUMO gaps as compared with N 4- and S,N3-porphyrins, which is reflected in the red-shifted absorptions, low oxidation potentials, and high reduction potentials of the phosphaporphyrins. The P-oxygenation of the P,X,N2-porphyrins with H2O2 has been found to lead to the formation of different types of products. The 18π P,N3-porphyrin was transformed into the 22π aromatic P(O), N3-porphyrin accompanied by the π extension at the peripheral C3 bridge, whereas the 18π P,S,N2-porphyrin was converted to the isophlorin-type 20π antiaromatic P(O),S,N2-porphyrin. In both of the reactions, simple P-oxygenated 18π P(O),X,N2-porphyrins were formed as the initial products, which were subsequently transformed into the 22π or 20π porphyrins. The two reaction courses from 18π to 20π/22π are apparently determined by the combination of the core heteroatoms (i.e., P,N3 or P,S,N2) and the structure of the peripherally fused carbocycles. The present results demonstrate that the incorporation of a phosphorus atom into the core is not only a highly promising way to modify the fundamental properties of the porphyrin 18π system but also a reliable tool to stabilize uncommon 22π and 20π systems through the chemical modifications at the core phosphorus atom. © 2009 American Chemical Society.

DOI： 10.1021/jo902060b

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The synthesis, structure, and electrochemical/optical properties of the zinc complexes of 5,10-porphodimethene-type thiophene-containing (S,N3-) and phosphole-containing (P,N3-) calixphyrins are reported. The S,N3- and P,N3-calixphyrin free bases react with zinc(II) salts to give the corresponding zinc complexes in good yields. The S,N3-calixphyrin-ZnI complex adopts a distorted square pyramidal geometry, with the S and N atoms at the basal positions. The S,N3-calixphyrin-ZnX complexes emit red fluorescence with fluorescent quantum yields up to 23%, whereas the P,N3-calixphyrin-ZnCl complex is weakly fluorescent. Among the first-row transition metals (Fe2+, Cu2+, and Zn2+) examined, the chelation-enhanced fluorescence is observed specifically for the Zn2+ ion. These results indicate that the 5,10-porphodimethene-type S,N3-hybrid calixphyrin is a promising turn-on fluorescent probe for Zn2+ sensing.

DOI： 10.1080/10426501003773431

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Chemical Society of Japan  

An oligothiophene bearing l-hydroxy-l-oxodithieno[2,3-b:3′,2′- d]phosphole (TP) as a novel anchoring group has been synthesized for dye-sensitized solar cells (DSSC). Attenuated total reflectance-Fourier transform infrared and X-ray photoelectron spectroscopy measurements disclosed the bidentate binding of the phosphinic acid unit to a TiO2 surface. A TPsensitized TiO2 cell yielded a maximum incident photon-tocurrent efficiency of 66% and a power conversion efficiency of 1.8%, indicating that 1-hydroxy-1-oxodithienophosphole is a potential unit as a new type of anchoring groups for DSSC. © 2010 The Chemical Society of Japan.

DOI： 10.1246/cl.2010.448

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DOI： 10.1039/c0cc00709a

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DOI： 10.1021/om900745t

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp907288h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The palladium complex of P,S-containing hybrid calixphyrin 1 was investigated with the DFT method. There are two kinds of valence tautomer in 1: one is a Pd(II) form in which the calixphyrin moiety possesses -2 charges and the Pd center takes +2 oxidation state, and the other is a Pd(0) form in which the calixphyrin is neutral and the Pd center takes zero oxidation state. Complex 1 takes the Pd(II) form in the ground state. Though the Pd center takes +2 oxidation state, DFT computations clearly show that the oxidative addition of phenyl bromide (PhBr) to 1 occurs with moderate activation enthalpy, as experimentally proposed. The first step of the oxidative addition is the coordination of PhBr with the Pd center to form intermediate 1INTa, in which the Pd center and the calixphyrin moiety are neutral; in other words, the valence tautomerization from the Pd(II) form to the Pd(0) form occurs in the palladium calixphyrin moiety. The activation enthalpy is 22.5 kcal/mol, and the enthalpy change of reaction is 20.3 kcal/mol. The next step is the C-Br sigma-bond cleavage of PhBr, which occurs with activation enthalpy of 2.0 kcal/mol relative to 1INTa. On the other hand, the oxidative additions of PhBr to palladium complex of P,S-containing hybrid porphyrin 2 and that of conventional porphyrin 3 need much larger activation enthalpies of 49.1 and 74.4 kcal/mol, respectively. The differences in the reactivity among 1, 2, and 3 were theoretically investigated; in 1, the valence tautomerization occurs with moderate activation enthalpy to afford the Pd(0) form which is reactive for the oxidative addition. In 2, the tautomerization from the Pd(II) form to the Pd(0) form needs very large activation enthalpy (43.3 kcal/mol). In 3, such valence tautomerization does not occur at all, indicating that the Pd(II) must change to the Pd(IV) in the oxidative addition of PhBr to 3, which is a very difficult process. These differences are interpreted in terms of the pi* orbital energies of P,S-containing hybrid calixphyrin, hybrid porphyrin, and conventional porphyrin and the flexibility of their frameworks.

DOI： 10.1021/ja901166a

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DOI： 10.1021/ol901194m

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DOI： 10.1021/ar900075e

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DOI： 10.1021/jp902001z

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DOI： 10.1021/jp902623g

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A novel strategy for constructing a vertical arrangement of bicontinuous donor-acceptor arrays on a semiconducting electrode has been developed. The relationship between the film structure and the photoelectrochemical properties has been elucidated as a function of the number of donor Layers for the first time. The maximum incident photon-to-current efficiency value (21%) is comparable to the highest value (20%) reported for vertical arrangements of bicontinuous donor-acceptor arrays on electrodes.

DOI： 10.1021/ja8096465

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.200900542

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The first comparative study on the optical and electrochemical properties of naphthalene, acenaphthene, and acenaphthylene fused phosphole derivatives, was reported. Naphthalene-, acenaphthene-, and acenaphthylene-fused phosphole derivatives 3-5 were successfully prepared by utilizing a TiII- mediated cyclization of dialkynylated naphthalene (2a), acenaphthene (2b), and acenaphthylene (2c). Treatment of gold(I) complexes 3b,c with excess P(NMe 2)3 afforded o3-P compounds 4b,c, which were subsequently oxidized by m-chloroperbenzoic acid (mCPBA) to the corresponding P-oxides 5b, c. At the last stage of this study, the electron mobility of vacuum-deposited films of 5a and 5b was studied by the time-of-flight (TOF) technique. The results demonstrate that the fusion of the naphthalene ring into the phosphole platform is a highly promising protocol to the development of a new class of phosphole based p-systems with high electron-transporting ability.

DOI： 10.1002/chem.200901378

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DOI： 10.1039/b819255n

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Substituent effects on the oxidizing ability of tetraarylbismuthonium tetrafluoroborates in alcohol oxidation are reported. Intermolecular and intramolecular competition experiments on geraniol oxidation by the combined use of tetraarylbismuthonium tetrafluoroborates and N,N,N',N'-tetrai-netramethylguanidine (TMG) have revealed that the oxidizing ability of the bismuthonium salt increases by the introduction of methyl groups at the ortho position and an electron-withdrawing group at the para position of the aryl ligands. The intermolecular and intramolecular H/D kinetic isotope effects observed for the competitive oxidation of p-bromobenzyl alcohols have shown that the present oxidation reaction consists of fast pre-equilibrium leading to alkoxytetraarylbismuth(V) intermediates (first step) and alpha-hydrogen abstraction by the aryl ligand attached to the bismuth (second step). The experimental results demonstrate that the electron-deficient aryl ligands enhance the electrophilicity at the bismuth center to put forward the first step and that the bulky ligands destabilize the alkoxybismuth(V) intermediates to accelerate the second step. The newly explored mesityl- and 2,6-xylyltriarylbismuthonium salts have proven to convert primary and secondary alcohols to the corresponding carbonyl compounds with high efficiency under mild conditions. A remark-able steric effect of these oxidants has also been exhibited in the chemoselective oxidation between primary and secondary benzylic alcohols.

DOI： 10.1246/bcsj.81.1621

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DOI： 10.1021/jp807991k

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DOI： 10.1039/b803272f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Fused five-membered zinc porphyrin carboxylic acid has been synthesized to improve light-harvesting capability in the visible and near-infrared regions. The fused porphyrin-sensitized TiO<SUB>2</SUB> cell exhibited the photocurrent generation extending over 800 nm, although the power conversion efficiency was found to be moderate (0.30%).

DOI： 10.1246/cl.2008.846

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/cphc.200800270

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Symmetric and asymmetric hybrid calixpyrroles containing a sigma(4)-phosphole or sigma(4)-2,3-dihydrophosphole unit (symmetric and asymmetric sigma(4)-P,N(2),X-hybrids: X = S, O) were prepared by using acid-promoted condensation reactions of the corresponding sigma(4)-phosphatripyrranes with 2,5-bis(1-hydroxy-1-methylethyl)heteroles. The X-ray crystallographic analyses of the symmetric and asymmetric sigma(4)-P,N(2),X-hybrids show that the cavity sizes of the sigma-P,N(2),S-hybrids are larger than those of the sigma(4)-P,N(2),O-hybrids, mainly reflecting the difference in edge-to-edge distances of the thiophene and furan rings. The symmetric sigma(4)-P,N(2),X-hybrids and the asymmetric sigma(4)-P,N(2),S-hybrid were successfully converted to the corresponding sigma(3) forms by reductive desulfurization at the phosphorus center. Each of the symmetric sigma(3)-P,N(2),X-hybrids was obtained as a mixture of two conformers, where the lone pair of the phosphorus atom is located inside (in) and outside (out) the cavity. The interconversion between the in and out type conformers of the asymmetric sigma(3)-P,N(2),S-hybrid was sufficiently slow to isolate each of them. The complexation reactions of the symmetric sigma(3)-P,N(2),S-hybrid with Au(I), Pt(II), and Pd(II) ions afforded both of the in and out type complexes, where the in type complexes were the thermodynamically favored products. In the complexation reactions of the asymmetric sigma(3)-P,N(2), S-hybrids, the stereochemistry at the phosphorus center was retained to give the in or out type complex exclusively. In the in-in type trans-M(II)-bis(phosphine) complexes (M = Pt, Pd) derived from the symmetric and asymmetric sigma(3)-P,N(2),S-hybrids, the M-Cl fragment is bound above the cavities of the two macrocycles. The crystal structures and the (1)H NMR spectra of these M(II) complexes reveal that the P,N(2),S-hybrid calixpyrroles bind the M-Cl fragments through P-M coordination and cooperative NH-Cl hydrogen-bonding interactions.

DOI： 10.1021/om800099h

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The synthesis, structure, and optical and electrochemical properties of thiophene-containing hybrid calixphyrins are reported. The 5,10-porphodimethene type 14 pi- and 16 pi-S,N(2),X-hybrid calixphyrins (X = NH, O, S) were prepared by acid-promoted dehydrative condensation between a thiatripyrrane and the corresponding 2,5-bis[hydroxy(phenyl)methyl]heteroles followed by DDQ oxidation. Both crystallographic and spectroscopic analyses of the newly prepared hybrid calixphyrins have revealed that the combination of heteroles explicitly influences the electronic structures of the pi-conjugated framework. The 14 pi-S,N(2),X-hybrid calixphyrins have proven to be fluorescent in solution.

DOI： 10.1021/jo800532n

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Photoirradiation of triaryl(1-pyrenyl)bismuthonium salts in acetonitrile afforded triarylbismuthanes and pyrene, accompanied by the generation of protic acids. Triaryl(1-pyrenyl)bismuthonium hexafluoroantimonates have proven to behave as efficient photoinitiators for cationic polymerization of oxiranes and a vinyl ether, affording the corresponding polymers in good yields within 1 min.

DOI： 10.1021/ol8005453

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

5,10,15,20-Tetrakis(2,4,6-trimethylphenyl)-6′-carboxyquinoxalino[2, 3-β]porphyrinatozinc (II) (ZnQMA) and 5,10,15,20-tetrakis(2,4,6- trimethylphenyl)-6′,7′-dicarboxyquinoxalino[2,3-β] porphyrinatozinc (II) (ZnQDA) have been synthesized to evaluate the effects of β,β′-carboxyquinoxalino moieties on the structure and optical, electrochemical, and photovoltaic properties of the porphyrins. Both ZnQMA and ZnQDA exhibited broadened and red-shifted light absorption in UV-visible absorption spectra compared with 5,10,15,20-tetrakis(2,4,6-trimethylphenyl) porphyrinatozinc (II) (ZnP). ZnQMA and ZnQDA also showed decrease in the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap due to the extension of the porphyrin π-system. From the results of 1H NMR spectroscopy and DFT calculations, ZnQMA and ZnQDA were found to adopt saddle and planar structures, respectively. ZnQMA-sensitized TiO 2 solar cell with TiO2 nanoparticles (P25) revealed the power conversion efficiency (η) of 5.2%, whereas ZnQDA-sensitized cell showed η = 4.0%. The superior performance of the ZnQMA-sensitized solar cell to the ZnQDA-sensitized one is originated from both the more favorable electron injection and charge collection efficiency. © 2008 American Chemical Society.

DOI： 10.1021/jp710400p

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Multiporphyrin-modified CdSe nanoparticles (CdSe-H2P) were prepared to elucidate the interaction between chromophores and luminescent semiconducting nonoparticles in the excited and ground states. The CdSe-H2P nanoparticles were obtained by place-exchange reactions of hexodecylamine-thiophenol-modified CdSe nanoparticles with porphyrin alkanethiols in toluene. The number of porphyrin molecules on the surface of a single CdSe nanoparticle increased with increasing reaction time to reach a saturated maximum of 21. The porphyrins as well as the core in CdSe-H2P can absorb UV/Vis radiation. Steady-state emission and emission-lifetime measurements reveal efficient energy transfer from the CdSe excited state to the porphyrins in the CdSe-H2P nanoparticles. The resulting porphyrin excited singlet state is not quenched by the CdSe core. These unique properties are in sharp contrast with those of multiporphyrin-modified metal and silica nanoparticles. Thus, semiconducting nanoparticle-multiporphyrin composites ore highly promising as novel artificial photosynthetic materials.

DOI： 10.1002/cssc.200700138

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The 18π-σ3- and 22π-σ4- phosphaporphyrins were successfully prepared by an acid-promoted condensation between a phosphatripyrrane and a 2,5-bis[hydroxy(phenyl)methyl]pyrrole, and their structures, aromaticity, and optical and electrochemical properties were disclosed. Notably, a σ4-phosphaporphyrinogen and the 18π-σ3-phosphaporphyrin undergo oxidative π-extension at the peripherally fused carbocycle to afford the 22π-σ4- phosphaporphyrin. © 2008 American Chemical Society.

DOI： 10.1021/ol7029118

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Bithiophene-fused benzo[c]phospholes were successfully prepared by a TiII-mediated cyclization of dialkynylated bithiophene derivatives. It was revealed that the optical and electrochemical properties of the bithiophene-fused benzo[c]phospholes are deeply related to the π-conjugation modes at the fused bithiophene subunits. Both experimental and theoretical results demonstrate that the appropriately ringannulated systems are potential emitters with small HOMOLUMO energy gaps covering the orange-to-red region due to the efficient π-electron derealization over the three conjugated heterole rings. © Wiley-VCH Verlag GmbH &amp
Co. KGaA, 2008.

DOI： 10.1002/ejoc.200701008

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DOI： 10.1021/ja076709o

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Core-modified isophlorin-metal complexes were successfully prepared by redox-coupled complexation of P,S,N2-hybrid porphyrin with zerovalent palladium, nickel, and platinum. In this transformation, the core-phosphorus atom plays crucial roles in enhancing the electron-accepting ability of the 18π porphyrin ring and stabilizing the 20π isophlorin ring owing to high P-M affinity. The isolated Pd and Pt complexes are chemically stable under ambient conditions. The Pd-P,S,N2 isophlorin complex was structurally characterized by X-ray crystallography, which revealed a distorted 20π plane with a square planar palladium(II) center. Experimental (1H, UV-vis, and X-ray) and theoretical (density functional theory calculations) results suggest that the P,S,N2-isophlorin-metal complexes possess nonaromaticity in terms of both magnetic and geometrical criteria. Copyright © 2008 American Chemical Society.

DOI： 10.1021/ja807742g

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DOI： 10.1021/ja710542e

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Three types of bithiophene-fused benzo[c]phospholes were successfully prepared by Ti(II)-mediated cyclization of the corresponding dialkynylated bithiophene derivatives as a key step. Each sigma(3)-phosphorus center of the benzo[c]phosphole subunits was readily transformed into sigma(4)-phosphorus center by Au coordination or oxygenation. In addition, the bithiophene subunit was functionalized at the alpha,alpha'-carbon atoms by Pd-catalyzed cross-coupling reactions with heteroarylmetals and by an S(N)Ar reaction with hexafluorobenzene. The experimentally observed results (NMR spectroscopy, X-ray analysis, UV/Vis absorption/fluorescence spectroscopy, and cyclic/differential-pulse voltammetry) have revealed that the structural, optical, and electrochemical properties of the bithiophene-fused benzo[c]phospholes vary considerably depending on the pi-conjugation modes at the bithiophene subunits and the substituents of the heterocyclopentadiene components. The appropriately ring-annulated sigma(3)-P derivatives and sigma(4)-P-AuCl complexes were found to emit fluorescence in the orange-red region, and the sigma(4)-P-oxo derivatives proved to undergo reversible one-electron reduction at -1.4 to -1.8V (vs ferrocene/ferrocenium). These results indicate that the bithiophene-fused benzo[c]phospholes possess narrow HOMO-LUMO gaps and low-lying LUMOs, which was confirmed by density functional theory calculations of their model compounds. The time-of-flight measurement of an ITO/benzo[c]phosphole/Al device showed that the electron mobility in the P-oxo derivative is one-order higher than that in Alq(3) at low electric fields. The present study demonstrates that the arene-fused benzo[c]phosphole skeleton could be a highly promising platform for the construction of a new class of phosphole-based optoelectrochemical materials.

DOI： 10.1002/chem.200801017

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DOI： 10.1002/asia.200800229

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/chem.200702053

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5323

DOI： 10.1021/jp805122z

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DOI： 10.1002/chem.200700446

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp0726079

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DOI： 10.1021/jo070822f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

DOI： 10.1016/j.cplett.2007.07.013

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DOI： 10.1021/jp072075w

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DOI： 10.1021/jp071604t

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

In the presence of N,N,N',N'-tetramethylguanidine, mesityltriphenylbismuthonium tetrafluoroborate oxidizes primary and secondary alcohols to aldehydes and ketones, respectively, under mild conditions. In this reaction, the mesityl ligand exclusively abstracts an alpha-hydrogen to afford mesitylene and triphenylbismuthane as side products. A remarkable steric effect has also been exhibited in the chemoselective oxidation between primary and secondary alcohols. (c) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2007.02.085

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Novel 5-(5-carboxy-2-thienyl)-10,15,20-tris(2,4,6-trimethylphenyl)- porphyrinatozinc(II) (Zn5S), 5-(5-carboxy-2-furyl)-10,15,20-tris(2,4,6- trimethylphenyl)porphyrinatozinc(II) (Zn5O), and 5-(4-carboxy-2-thieny 1)-10,15,-20-tris(2,4,6-trimethylphenyl)porphyrinatozinc(II) (Zn4S) were synthesized to evaluate the spacer effects on the structures of the porphyrin films and the photovoltaic properties of the porphyrin-sensitized TiO 2 solar cells. Each of the porphyrins showed different adsorption behavior and saturated coverage on the TiO2 surface and photovoltaic properties depending on the identity of heteroatoms in the bridge and the position of carboxylic acid. Specifically, Zn5S-sensitized TiO2 cell displayed larger, maximum incident photon-to-current efficiency of 65% and maximum power conversion efficiency of 3.1% than Zn5O-sensitized TiO2 cell by ∼20% and ∼ 40%, respectively. We interpret that these results are stemmed from ancillary electron-transfer pathway through specific interaction between a sulfur atom in the bridge of Zn5S and the TiO2 surface. Optical spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, density functional theory calculations, and photovoltaic measurements under standard AM 1.5 conditions were employed to support our proposal. © 2007 American Chemical Society.

DOI： 10.1021/jp067290b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/ol070556s

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The synthesis, structures, and optical and electrochemical properties of meso-phosphorylporphyrins are described. The copper-catalyzed carbon-phosphorus cross-coupling reaction of a meso-iodoporphyrin with di-n-butyl phosphite and diphenylphosphane oxide has proved to be an efficient and general method for the synthesis of meso-phosphorylporphyrins. Zinc phosphorylporphyrins thus obtained readily undergo self-organization through Poxo-Zn coordination to form noncovalently linked, cofacial porphyrin dimers or linear olicyomers, which have been characterized by spectroscopic methods and X-ray crystallographic analyses. In toluene, CH2Cl2, and CHCl3, the zinc phosphorylporphyrins exist mostly as dimers or monomers, depending on their concentrations, the temperature, and the presence of additives. The self-association constants for dimerization in toluene have been determined by UV/Vis absorption titration measurements. The meso-diphenylphosphorylporphyrin dimer displays excitonic coupling of the Soret band with a splitting energy of 940 cm(-1). Fluorescence lifetimes of the zinc phosphorylporphyrins have been found to be affected only slightly by the concentration of the solution, and by the addition of triphenylphosphane oxide, suggesting that the effect of dimerization on their photodynamics in the S, state is negligible. On the other hand, the effect of dimerization is clearly reflected in their electrochemical oxidation processes, as the initially produced radical cations are efficiently delocalized over the two porphyrin rings. These findings demonstrate the potential utility of meso-phosphorylporphyrins as new models for the special pair in photosynthesis and as new building blocks for porphyrin-based supramolecular materials.

DOI： 10.1002/chem.200600835

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The synthesis and aggregation behavior of meso-sulfinylporphyrins are described. The copper-catalyzed C-S cross-coupling reaction of a meso-iodoporphyrin with benzenethiol and n-octanethiol has proved to be an efficient method for the synthesis of meso-sulfanylporphyrins, which are oxygenated by m-chloroperbenzoic acid to produce the corresponding meso-sulfinylporphyrins. Optically active zinc meso-sulfinylporphyrins were successfully isolated by means of optical resolution of the racemates on a chiral HPLC column. Zinc sulfinylporphyrins readily undergo self-organization through S-oxo-zinc coordination to form cofacial porphyrin dimers in solution, in which the hetero- and homodimers are present as a diastereomeric mixture. The aggregation modes of the S-oxo-tethered porphyrin dimers were fully characterized by 1H NMR, IR, and UV/Vis spectroscopy as well as DFT calculations on their model compounds, thus revealing that the self-aggregation behavior depends on the combination of S chirality. The absolute configurations at the sulfur center can be determined by the exciton-coupled CD method. The observed self-association constant for the S-oxo-tethered dimerization of (S)-phenylsulfinylporphyrin in toluene is larger than that in dichloromethane, which reflects the difference in dipole moments between the homodimer and the monomer. In cyclic and differential pulse voltammetry, the first oxidation process of the cofacial dimers is split into two reversible steps, which indicates that the initially produced π radical cations are delocalized efficiently between the two porphyrin rings. The present findings demonstrate the potential utility of meso-sulfinyl groups as promising ligands for investigating the effects of peripheral chirality on the structures and optical and electrochemical properties of metal-assisted porphyrin self-assemblies. © 2007 Wiley-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

DOI： 10.1002/asia.200700191

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

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DOI： 10.1021/jp068893q

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A phosphorus-containing hybrid porphyrin was successfully prepared via the BF3-promoted dehydrative condensation between sigma(4)-phosphatripyrrane and 2,5-bis[hydroxy(phenyl)methyl]thiophene. The NMR and UV-vis absorption spectra, electrochemical measurements, and DFT calculations revealed that the sigma(3)-P,N-2,S-hybrid porphyrin exhibits high aromaticity as an 18 pi-electron system in terms of both geometric and magnetic criteria.

DOI： 10.1021/ol622763

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/la061527d

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DOI： 10.1021/ja0640039

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DOI： 10.1002/adma.200600312

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ol061506a

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Symmetrically and unsymmetrically 2,5-difunctionalized phospholes bearing ester groups were prepared in a one-pot procedure from the corresponding diynes and dichloro-(phenyl) phosphine via titanacyclopentadienes. The observed optical properties of the functionalized phospholes show that the pi-conjugative push-pull interaction between the 2- and 5-substituents plays an important role in controlling the light-emitting efficiency.

DOI： 10.1021/jo0605748

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Clusters of phthalocyanine and phthalocyanine-perylene diimide have been prepared and electrophoretically deposited on nanostructured SnO(2) electrodes. The structure and photoelectrochemical properties of the clusters have been investigated by using UV-visible absorption, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoelectrochemical and photodynamical measurements. Enhancement of the photocurrent generation efficiency in the composite system has been achieved relative to that in the phthalocyanine reference system without the perylene diimide. Such information will be valuable for the design of molecular photoelectrochemical devices that exhibit efficient photocurrent generation.

DOI： 10.1021/la0533314

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DOI： 10.1021/om060300a

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DOI： 10.1021/jp061524+

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Structure and photoelectrochemical properties of nanostructured SnO(2) electrodes deposited electrophoretically with the composite clusters of porphyrin-modified gold nanoparticle with a long, flexible spacer and C(60) molecules have been examined to obtain basic information on the development of organic solar cells with a high performance. The photoelectrochemical system with the long, flexible spacer between the porphyrin and the gold nanoparticle in the porphyrin-modified gold nanoparticle exhibited comparable external quantum yield in the UV-vis regions relative to porphyrin-modified gold nanoparticle with a relatively short spacer-C(60) Composite reference system. These results demonstrate that a suitable spacer to incorporate C(60) molecules efficiently between the porphyrins in porphyrin-modified gold nanoparticles is a prerequisite for improving the performance of porphyrin and fullerene-based organic solar cells. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2005.05.109

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A silica microparticle has been successfully employed as a nanoscaffold to self-organize porphyrin and C-60 molecules on a nanostructured SnO2 electrode which exhibits efficient photocurrent generation.

DOI： 10.1039/b513707a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/la0533314

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Novel gold nanoparticles modified with a mixed self-assembled monolayer of porphyrin alkanethiol and short-chain alkanethiol were prepared (first step) to examine the size and shape effects of surface holes (host) on porphyrin-modified gold nanoparticles. ne porphyrin-modified gold nanoparticles with a size of about 10 nm incorporated C-60 molecules (guest) into the large, bucket-shaped holes, leading to the formation of a supramolecular complex of porphyrin-C-60 composites (second step). Large composite clusters with a size of 200400 nm were grown from the supramolecular complex of porphyrin-C-60 composites in mixed solvents (third step) and deposited electrophoretically onto nanostructured SnO2 electrodes (fourth step). Differences in the porphyrin:C-60, ratio were found to affect the structures and photoelectrochemical properties of the composite clusters in mixed solvents as well as on the SnO2, electrodes. The photoelectrochemical performance of a photoelectrochemical device consisting of SnO2 electrodes modified with the porphyrin-C-60 composites was enhanced relative to a reference system with small, wedged-shaped surface holes on the gold nanoparticle, Time-resolved transient absorption spectroscopy with fluorescence lifetime measurements suggest the occurrence of ultrafast electron transfer from the porphyrin excited singlet states to C-60 or the formation of a partial charge-transfer state in the composite clusters of supramolecular complexes formed between porphyrin and C-60 leading to efficient photocurrent generation in the system. Elucidation of the relationship between host-guest interactions and photoelectrochemical function in the present system will provide valuable information on the design of molecular devices and machines including molecular photo-voltaics.

DOI： 10.1002/chem.200500610

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Two kinds of fullerene derivatives have been designed to examine the effect of the fullerene substituents on the structure and photoelectrochemical properties of fullerene clusters electrophoretically deposited on nanostructured SnO2 electrodes. The cluster sizes increase and the incident photon-to-current efficiencies decrease with introduction of large substituents into C-60. The trend for photocurrent generation efficiency as well as surface morphology on the electrode can be explained by the steric bulkiness around the C-60 molecules. A C-60 molecule with two alkoxy chains is suggested to give a bilayer vesicle structure, irrespective of the hydrophobic nature of both the C-60 and alkoxy chain moieties. Such information will be valuable for the design of photoactive molecules, which are fabricated onto electrode surfaces to exhibit high energy conversion efficiency.

DOI： 10.1021/jp044725r

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/adma.200401770

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/jp0537409

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/jp044725r

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/chem.200500610

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jo0485740

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A systematic series of triarylbismuthane oxides was prepared in order to disclose their structure and reactivity, which have been compared with those of lighter pnictogen counterparts. X-ray crystallographic analysis of tris(2-methoxyphenyl)bismuthane oxide and tris(2-methoxyphenyl)stibane oxide revealed that they exist as dimers with a flat bis(a-oxo) ring, implying that the polarized Bi+-O- and Sb+-O- bonds aggregate to attain electrostatic stabilization. In sharp contrast to their phosphorus, arsenic, and antimony counterparts, triarylbismuthane oxides are thermally unstable and possess a high oxidizing ability. In particular, the bismuthane oxides bearing ortho-substituted aryl ligands oxidized primary and secondary alcohols to aldehydes and ketones, respectively, with high efficiency under mild conditions.

DOI： 10.1021/om0494115

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jo0492721

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Self-assembled monolayers (SAMs) of porphyrins have been prepared to examine the substituent effects of porphyrin monolayers on the structure and photoelectrochemical properties of the SAMs on an ITO electrode. The ultraviolet (UV)-visible absorption, steady-state fluorescence, and cyclic voltammetry measurements for the porphyrin SAMs revealed that the interaction between the porphyrins without bulky tert-butyl groups is much larger than that of the porphyrins with bulky tert-butyl groups. Photoelectrochemical measurements were performed in nitrogen-saturated Na2SO4 aqueous solution containing triethanolamine as an electron sacrificer using the modified ITO working electrode, a platinum wire counter electrode, and an Ag/AgCl reference electrode. The internal quantum yields of photocurrent generation together with the porphyrin fluorescence lifetimes rernain virtually the same irrespective of the steric hindrance, which is in sharp contrast with severe self-quenching of the porphyrin excited singlet state in conventional molecular assemblies such as Langmuir-Blodgett films. The two-dimensional, densely packed structure of the porphyrins in SAM is responsible for the long-lived excited singlet state, which is similar to the antenna function of photosystem I in cyanobacteria. These results will provide valuable information on the construction of artificial light-harvesting systems.

DOI： 10.1021/jp037625e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A hydrogen bonding effect on photocurrent generation has been evaluated successfully in a mixed film of porphyrin and fullerene with hydrogen bonding on an ITO electrode, which exhibits efficient cathodic photocurrent generation as compared to the reference system without hydrogen bonding.

DOI： 10.1039/b404690k

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Language：English   Publisher：Elsevier  

We have proposed a novel strategy for artificial photosynthesis where porphyrins and fullerenes are assembled as building blocks into nanostructured artificial photosynthetic systems by the help of self-assembled monolayers. Photodynamical studies on porphyrin-fullerene-linked systems revealed that fullerenes accelerate photo-induced electron transfer and charge-shift and slow down charge recombination, which is in sharp contrast with the modalities of conventional two-dimensional aromatic acceptors such as quinones and imides. We proposed and demonstrated, for the first time, that such electron transfer properties are attributable to the small reorganization energies of fullerenes, which make it possible to optimize artificial photosynthetic multistep charge separation. The multistep electron transfer strategy was combined with our finding that fullerenes have small reorganization energies, which are well-suited for the construction of light energy conversion systems as well as artificial photosynthetic models. Highly efficient photosynthetic energy and electron transfers were realized at gold and indium-tin oxide (ITO) electrodes modified with self-assembled monolayers of porphyrin-fullerene-linked systems. Porphyrin-modified gold nanoclusters were found to have potential as artificial photosynthetic materials and photonic molecular devices. These results provide basic principles and concepts for the development of nanostructured artificial photosynthetic materials as well as molecular devices. © 2003 Japanese Photochemistry Association. Published by Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1389-5567(03)00004-2

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Triarylphosphanes 1 (Ar3P
Ar = Ph, 4-MeC6H4), triphenylarsane (2), and triarylstibanes 3 (Ar3Sb
Ar = 2-MeC6H4, 2-MeOC6H4) reacted with trifluoromethanesulfonamide (7a) in the presence of equimolar diethyl azodicarboxylate to afford the corresponding triaryl(sulfonylimino)pnictoranes [Ar3M=NSO2CF3
8 (M = P), 9 (M = As), 10 (M = Sb)]. The Kirsanov-type reaction of triarylantimony dichlorides 5 (Ar3SbCl2
Ar = 2-MeC6H4, 2-MeOC6H4) and triarylbismuth dichlorides 6 (Ar3BiCl2
Ar = 2-MeC6H4, 2-MeOC6H4, 2,4,6-Me3C6H2) with sulfonamides 7 (H2NSO2R
R = CF3, 4-MeC6H4, Me) in the presence of 2 equiv of potassium tert-butoxide yielded triaryl(sulfonylimino)-λ5-stibanes 10 and -bismuthanes 11, respectively. The ortho-substitution in aryl ligands of 10 and 11 has been found to bring about considerable kinetic stabilization of the reactive Sb=N and Bi=N bonds. A structural comparison was made for a series of triaryl(sulfonylimino)pnictoranes 8-11 by IR spectroscopy and X-ray crystallography. In the IR spectra of 9-11, SO2 asymmetric stretching absorptions (νSO2) were observed at lower wavenumbers as compared to those of phosphorus counterparts 8. The difference in frequency (δνSO2) from 8 increased progressively as the pnictogen element being utilized moved down the group 15 column on the periodic table. X-ray crystallographic analyses of eight of the triaryl(sulfonylimino)pnictoranes prepared confirmed the increasing single-bond character of the M=N bond, with the contribution from the canonical structure M+-N=S(O)-O- increasing in importance in the order P &lt
As &lt
Sb &lt
Bi. Among all triaryl(sulfonylimino)pnictoranes examined, only imino-λ5-bismuthanes 11 oxidized alcohols to carbonyl compounds.

DOI： 10.1021/ic0110575

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEORG THIEME VERLAG KG  

Triarylbismuth(V)-oxo and -hydroxo compounds react with organoboronic acids and esters in the presence of (BF3OEt2)-O-. to afford the corresponding bismuthonium salts. They also undergo dehydrative coupling with cyclic 1,3-dicarbonyl compounds, amides and sulfonamides to give stabilized bismuthonium ylides, bismuthane N-acylimides and bismuthane N-sulfonylimides, respectively. All reactions proceed efficiently under mild conditions.

DOI： 10.1055/s-2002-23536

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

High efficiency and chemoselectivity as well as the facile isolation of the carbonyl products by simple workup procedures characterize a new method of alcohol oxidation. A variety of primary and secondary alcohols are oxidized to aldehydes and ketones by the combined use of tris(2-methylphenyl)bismuth dichloride and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) under mild conditions [Eq. (1)].

DOI： 10.1002/1521-3773(20020816)41:16<3028::AID-ANIE3028>3.0.CO;2-U

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/ic0110575

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

The synthesis, structure, and reactions of (acylimino)triaryl-λ5-bismuthanes and a comparative study of the structure and reactivity of a series of (acylimino)pnictoranes are reported. Treatment of ortho-substituted triarylbismuth dichlorides 1 (Ar3BiCl2
Ar = 2-MeC6H4, 2-MeOC6H4, 2,4,6-Me3C6H2) with amides 2 (H2-NCOR
R = CF3, CCl3, 3,5-(CF3)2C6H3) in the presence of 2.2 equiv of KO-t-Bu in dichloromethane afforded (acylimino)triaryl-λ5-bismuthanes 3 (Ar3Bi=NCOR) in yields of 77-96%. The ortho-substituted aryl ligands and the electron-withdrawing N-substituents afford kinetic and thermodynamic stabilization, respectively, to the reactive Bi=N bond. The structures and properties of a series of (acylimino)pnictoranes (Ar3M=NCOR and H3M=NCOCF3
M = P, As, Sb, Bi) are compared by IR and 13C and 15N NMR, X-ray crystallography, and ab initio molecular orbital calculations. It was found that the contribution of the M+-N=C-O- canonical form becomes more prominent and the single-bond character of the M=N bond increases progressively as the pnictogen atom becomes heavier. The Bi=N bond of (acylimino)-λ5-bismuthanes 3 possesses a highly polarized single-bond character, probably due to the differences in orbital size and electronegativity between the bismuth and nitrogen atoms. Thermal decomposition of (aroylimino)triaryl-λ5-bismuthane 3f (o-Tol3Bi=NCOAr
Ar = 3,5-(CF3)2C6H3) produces a gel in dry conditions or aniline 12 (ArNH2) in slightly wet conditions with a good recovery of tris(2-methylphenyl)bismuthane (4a). It is likely that the aryl isocyanate 13 (ArNCO) is produced during the thermolysis via a concerted C → N migration of the Ar group with an elimination of the triarylbismuthonio group as bismuthane 4a. (Acylimino)triaryl-λ5-bismuthanes 3 oxidize 1,1,2,2-tetraphenylethanediol, benzenethiol, methanol, and ethanol to benzophenone, diphenyl disulfide, methyl formate, and acetaldehyde, respectively, in two different reaction pathways depending on the structure of the substrates. Compound 3d (o-Tol3Bi=NCOCCl3) transfers the nitrenoid moiety to triphenylphosphane, triphenylarsane, and tris(2-methylphenyl)stibane to give the corresponding (acylimino)pnictoranes (Ar3M=NCOCl3
M = P, As, Sb) and 4a, suggesting that 3d is thermodynamically much less stable than their lighter pnictogen counterparts. The copper-catalyzed decomposition of 3 (o-Tol3Bi=NCOR) afforded N-acyl-o-toluidines 18 (o-TolNHCOR) via a Bi → N migration of the tolyl group. The observed reactivities of (acylimino)triaryl-λ5-bismuthanes 3 demonstrate a good leaving ability of the bismuthonio group.

DOI： 10.1021/ja003623l

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Language：Japanese   Publisher：The Society of Synthetic Organic Chemistry, Japan  

The syntheses and reactions of bismuthonium salts and bismuth ylides are reported. Various types of bismuthonium salts bearing a Bi-C<I><SUB>sp</SUB></I><I><SUP>3</SUP></I>, Bi-C<I><SUB>sp</SUB></I><I><SUP>2</SUP></I>, or Bi-C<I><SUB>sp</SUB></I> bond have been prepared by the Lewis-acid promoted reaction of triphenylbismuth difluoride with organometallic reagents. The bismuthonium salts thus obtained behave as alkyl cation equivalents, alkenyl cation equivalents, and carbene precursors. The bismuth ylides bearing a carbonyl group at the ylidic carbon react with carbonyl compounds to undergo epoxidation, transposition, or ring expansion depending on the structure of the substrates employed. These reaction modes are characteristic of bismuth among the group 15 elements. The stabilized bismuth ylides bearing a highly cross-conjugated ylidic carbon decompose, at an elevated temperature or in the presence of a copper catalyst, to give trisubstituted oxazoles. The observed unique reactivities of the bismuthonium salts and the bismuth ylides are ascribed to the good leaving ability of the triarylbismuthonio group.

DOI： 10.5059/yukigoseikyokaishi.59.834

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Other Link： https://jlc.jst.go.jp/DN/JALC/00122798045?from=CiNii

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEORG THIEME VERLAG KG  

Triarylbismuthanes bearing a vinyl, formyl, or acetyl group have been prepared in good yield via the directed ligand coupling of oxazoline-substituted tetraarylbismuthonium salts. Radical polymerization of the resulting diaryl(4-vinylphenyl)bismuthanes produced bismuth-containing polystyrenes soluble in organic solvents.

DOI： 10.1055/s-2001-14565

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DOI： 10.1021/ja010584k

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The reaction of iminotriaryl-lambda(5)-bismuthanes (2; Ar3Bi=NR; R = COR " or SO2R ") with dialkyl acetylenedicarboxylates (3; R'O2CC=CCO2R') has been found to afford highly stabilized bismuthortium ylides (4; Ar3Bi=C(CO2R')-C(CO2R')=NR) in 50-92% yield. The X-ray crystallographic analyses of two of these ylides demonstrated that their bismuth center possesses a distorted tetrahedral geometry with the highly cross-conjugated ylidic carbon atom. The observed Bi-C-ylide bond lengths of 2.178(7)-2.199(7) Angstrom are close to ordinary Bi-C-Ar bond lengths, suggesting an appreciable single bond character of the Bi-C-ylide bond. The action of two equivalents of acetic acid, hydrogen chloride, or 4-nitrophenol on 4 cleaved the Bi-C-ylide bond to give the corresponding triarylbismuth(V) compounds of the type Ar3BiX2 and olefins (5; R'O2CCH=C(CO2R')NHR). 4-Nitrobenzenethiol was oxidized by 0.5 equivalents of 4 to give bis(4-nitrophenyl) disulfide with a good recovery of triarylbismuthane 6 and olefin 5. On thermolysis at 200 degrees C, or when decomposed in the presence of a copper catalyst at room temperature, the ylides 4 bearing an N-aroyl group gave 2,4,5-trisubstituted oxazoles 7 and triarylbismuthanes 6 in moderate to excellent yields. (C) 2000 Elsevier Science S.A. All rights reserved.

DOI： 10.1016/S0022-328X(00)00295-3

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Rhenium-oxo complexes with the hydridotris(3,5-dimethyl-1-pyrazolyl)borate (Tp*) ligand are described. Halide complexes Tp*Re(O)X(Cl) (X = Cl, I) are prepared by treatment of Tp*Re(O)(OH)Cl with HX. Reaction of Tp*Re(O)Cls (3) with 1 or 2 equiv of LiPh/ZnCl2 or Et2Zn produces the corresponding oxo-aryl and oxo-alkyl complexes Tp*Re(O)(Ph)Cl, Tp*Re(O)(Ph)(2), and Tp*Re(O)(Et)Cl. Alkoxide complexes Tp*Re(O)(OR)CI and Tp*Re(O)(OR)(2) are prepared from 3 and ROH, PhOH, or catechol, Triflate complexes Tp*Re(O)X(OTf) (X = halide, H, Et, Ph, Oft, OPh) have been prepared by halide metathesis with AgOTf or by alkoxide metathesis with Me3SiOTf. Hydride complexes Tp*Re(O)(H)X (X = Cl, H) are generated from the corresponding alkoxide complexes with BH3. THF. Oxidation of Tp*Re(O)Ph(OTf) with Me2SO gives a phenoxide complex, and oxidation of Tp*Re(O)Et(OTf) with pyridine N-oxide gives acetaldehyde, Both reactions are similar to oxidations of related Tp compounds. Tp*Re(O)H(OTf) is oxidized by either reagent to Tp*Re(O)(3), with liberation of H+; such a hydride complex has not been accessible in the Tp system. The Tp* ligand imparts added stability to the rhenium(V) derivatives, making preparations easier. Steric constraints of the Tp* ligand are illustrated by the lack of phenyl and pyridine ligand rotation on the NMR time scale. The stability and crowding of the Tp* compounds inhibits reactions with oxygen atom donors so that heating is often required, and the resulting oxidations are more complex than for analogous Tp compounds.

DOI： 10.1021/om000133t

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Treatment of triarylbismuth difluorides 2 (Ar3BiF2; a, Ar = Ph; b, Ar = 4-MeC6H4; c, Ar = 4-MeOC6H4; d,Ar = 2-MeOC6H4) with methylboronic acid (3) in the presence of BF3. OEt2 in CH2Cl2 afforded the corresponding triaryl(methyl)bismuthonium tetrafluoroborates 4a-d ([Ar3MeBi+][BF4-]) in 42-91% yield. X-ray crystallographic analysis of compound 4d revealed that the bismuth center possesses a distorted tetrahedral geometry with C-Bi-C bond angles of 106.1(3)-113.6(3)degrees and Bi-C bond lengths of 2.182(7)-2.195(8) Angstrom. Compound 4a transferred the methyl group to Ph3E (E = P, As, Sb), tris(4-methylphenyl)bismuthine, ROH (R = Me, Et, i-Pr, PhCH2), water, sodium benzenesulfinate, sodium benzoate, N,N-dimethylformamide (DMF), and thioacetamide to give the corresponding methylated products with a good recovery of triphenylbismuthine. The pseudo-first-order rate constant (k(obsd) = 2.9 x 10(-4) s(-1)) observed for the reaction between 4a and benzyl alcohol (5d) was about twice as large as that (k(obsd) = 13 X 10(-4) s(-1)) between MeOTf and 5d (in CDCl3 at 23 degrees C; [4a] or [MeOTf] = 0.062 M; [5d] = 0.97 M). The observed reactivity of 4a clearly demonstrates the high nucleofugality of the triphenylbismuthonio group.

DOI： 10.1021/om000095d

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Triaryl (trifluoromethylsulfonylimino)-λ5-stibanes (Ar3-Sb=NSO2CF3) were prepared by the Kirsanov-type reaction of triarylantimony dichlorides with CF3SO2NH2 in the presence of KO-t-Bu and by the redox condensation of triarylstibines with CF3SO2NH2 in the presence of diethyl azodicarboxylate. The Sb = N bond of these monomeric imino-λ5-stibanes was found to possess moderate single-bond character owing to the resonance hybridization with the electron-withdrawing N-sulfonyl group.

DOI： 10.1021/ic991120e

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Treatment of triphenylbismuth difluoride with alkynyldiisopropoxyboranes in the presence of BF3. OEt2 in CH2Cl2 gives alkynyltriphenylbismuthonium tetrafluoroborates, which react with sodium p-toluenesulfinate in dual reaction modes depending on the solvents employed.

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Cyclic voltammetry has been used to study the electrochemical properties of 29 isoelectronic and isostructural osmium(VI)-nitrido, rhenium(lr)-oxo, and rhenium(V)-imido complexes of the form Tp(()*M-)(E)(X)(Y) [Tp(()*()) = Tp, HB(pz)(3); or Tp*, HB(3,5-Me(2)pz)(3)]. Oxidations from d(2) to d(1) species are typically reversible or quasi-reversible, while reductions to d(3) species are usually irreversible. The E-1/2 values for oxidation vary from &gt; + 2 V for TpOs(N)(Cl)(2) to - 0.11 V for TpRe(Ntolyl)(Ph)(Me) (vs. Cp2Fe+ , 0 in MeCN/(Bu4NPF6)-Bu-n). The potentials follow simple trends, Os(N) &gt; Re(O) &gt; Re(Ntolyl) and Tp &gt; Tp*. Potentials for TpM(E)(X)(Y) are also affected by the X and Y ligands, with OTf &gt; Cl congruent to I &gt; Ph &gt; alkyl, correlating with the Hammett a values for X and Y. In contrast, peak potentials for reduction of the compounds (ca. - 1.0 to - 1.5 V) do not follow simple patterns. The reactivity of these complexes as inner-sphere oxidants does not correlate with their peak reduction potentials. Rather. the ease of oxidation of the compounds better parallels their reactivity as oxidants. (C) 1999 Elsevier Science S.A. All rights reserved.

DOI： 10.1016/S0022-328X(99)00506-9

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The synthesis and stereochemical behavior of unsymmetrical tetraarylbismuthonium salts were investigated. Two methods (tin and boron methods) for synthesizing unsymmetrically substituted tetraarylbismuthonium salts were developed. In the tin method, successive treatment of triarylbismuth difluorides (1; (Ar3BiF2)-Bi-1) with trimethylsilyl cyanide and aryltri-n-butylstannanes (2; Bu3SnAr2) in the presence of a Lewis acid (BF3. OEt2 or Me3SiOTf) in boiling dichloromethane afforded tetraarylbismuthonium salts (3, [(Ar3ArBi+)-Ar-1-Bi-2][BF4-], or 5, [(Ar3ArBi+)-Ar-1-Bi-2][OTf-]) in 44-85% yield. In contrast, in the boron method, similar treatment of 1 with arylboronic acids (4; (ArB)-B-2(OH)(2)) in the presence of BF3. OEt2 afforded the tetrafluoroborates 3 in 55-99% yield at room temperature. Both methods were used to synthesize unsymmetrical tetraarylbismuthonium salts (9; (ArArArArBi+)-Ar-1-Ar-2-Ar-3-Bi-4][BF4-]) starting from unsymmetrical triarylbismuth difluorides 8. The boron method was also used. to synthesize unsymmetrical tetraarylbismuthonium tetrafluoroborates 14 bearing an oxazoline group at the ortho position ([(4-MeOC6H4)(4-CF3C6H4)(2-OxC(6)H(4))ArBi+][BF4-]; Ox = 4,4-dimethyl-3,4-dihydrooxazol-2-yl; a, Ar = 4-MeC6H4; b, Ar = 2-C4H3S). The reaction of bismuthonium tetrafluoroborate 14b with ammonium tosylate afforded bismuthonium tosylate 15, which, on treatment with sodium halides, was converted to the corresponding halides 16 ([(4-MeOC6H4)(4-CF3C6H4)(2-OxC(6)H(4))(2-C4H3S)Bi+][X-]; a, X = Cl; b, X = Br; c, X = I). Tetrafluoroborates 14 and tosylate 15 are thermally stable, but halides 16 are unstable and underwent ligand coupling in solution. The X-ray diffraction analysis of a tetrafluoroborate 20 ([(4-MeC6H4)(3)(2-OxC(6)H(4))Bi+][BF4-]) revealed a distorted tetrahedral geometry at the bismuth center, which was coordinated by the neighboring oxazoline nitrogen atom. The stereochemical behavior of the synthesized bismuthonium salts was investigated, The signals due to the diastereotopic geminal methyl groups on the oxazoline ring of 14 and 15 did not coalesce in the H-1 NMR spectra in 1,2;dichlorobenzene-d(4) (up to 150 degrees C), in DMSO-d(6) (up to 135 degrees C), and in pyridine-d(5) (up to 110 degrees C), whereas those of chloride 16a and bromide 16b coalesced in pyridine-d(5), 1,2-dichlorobenzene-d(4), chlorobenzene-d(5), and toluene-d(8). The coalescence temperature (T-c) depended on the nucleophilicity of the counteranions as well as on the polarity of the solvents; T-c decreased as the nucleophilicity of the counteranions increased or as the polarity of the solvent decreased. Thus, the configuration at bismuth in tetrafluoroborates 14 and tosylate 15 was found to be stable, whereas that in halides 16 strongly depended on the solvent polarity.
The observed permutation of bismuthonium halides, [(ArArArArBi+)-Ar-1-Ar-2-Ar-3-Bi-4][X-], can be explained by a pseudorotation mechanism involving a nonionic pentacoordinate species of the type (ArArArArBiX)-Ar-1-Ar-2-Ar-3-Bi-4.

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Treatment of the d(2) rhenium tolylimido complex TpRe(NTol)X-2 with RMgX, RLi, or organozinc reagents yields TpRe(NTol)(R)X [R = Ph, Me,-Et, i-Pr, n-Bu; X = Cl or I; Tol = p-tolyl; Tp = hydrotris(1-pyrazolyl)borate] or TpRe(NTol)R-2 (R = Ph, Me). Iodide for triflate metathesis with AgOTf yields TpRe(NTol)(X)OTf [X = Ph, Et, Cl, OTf (=OSO2CF3)]. Reaction of TpRe(NTol)(Et)I with excess rather than stoichiometric AgOTf generates the ethylene hydride cation [TpRe(NTol)(eta(2)-C2H4)(H)][OTf], which slowly rearranges by ethylene insertion to form TpRe(NTol)(Et)OTf. Treatment of TpRe(NTol)(Ph)I with AgPF6 gives not iodide abstraction but rather [{TpRe(NTol)(Ph)I}(2)Ag][PF6], with two Re-I-Ag linkages. Excess pyridine (py) slowly displaces triflate in TpRe(NTol)Ph(OTf) (11) to give [TpRe(NTol)Ph(py)][OTf]. The reaction is first-order in 11 and first-order in py. Triflate substitution is similarly slow in the oxo-Tp* derivative, Tp*Re(O)Ph(OTf) [Tp* = HB(3,5-Me(2)pz)(3)]. These reactions are many orders of magnitude slower than substitution in the oxo-Tp derivative TpRe(O)Ph(OTf). Kinetic and mechanistic data rule out dissociation of triflate ion in or before the rate-determining step and are most consistent with an associative pathway, Reaction with 1,10-phenanthroline gives the k(2)-Tp complex [K-2-TpRe(NTOl)Ph(phen)][OTf], indicating the lability of one arm of the Tp ligand. TpRe(NTol)Ph-2, TpRe(NTol)Me-2, TpRe(NTol)(Ph)OTf, TpRe(NTol)(OTf)(2), [{TpRe(NTol)(Ph)I}(2)Ag][PF6], and [K-2-TpRe(NTol)Ph(phen)] [OTf] have been structurally characterized. The imido ligand is a better electron donor and has a smaller trans influence than an oxo group in this system.

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The reactive Bi(V)=N bond in (acylimiao)triaryl-lambda(5)-bismuthanes has been found to be stabilized effectively by ortho-substituted aryl ligands such as o-tolyl, o-anisyl, and mesityl groups, These imino-lambda(5)-bismuthanes, in which the bismuth center possesses a distorted tetrahedral geometry, behave-as ct nitrene precursor as well as an oxidizing agent, depending on the substrates and conditions.

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Triphenylbismuthonium 2-oxoalkylides 2, generated in situ from bismuthonium salts 1 and a base in THF at low temperature, react with alpha-keto esters 3 and alpha-dikerones 6 to give oxiranes 4 or 7 and/or O-aroyl enolates of unsymmetrical beta-diketones 8, depending on the structures of substrates. Similar treatment of 2 with o-quinones 10 results in the ring expansion to 2-acyl-3-hydroxytropones 11. The enolates 8 and tropones 11 are most likely to be formed via the 1,2-carbon-to-oxygen and carbon-to-carbon migrations of the acyl group, respectively, both under simultaneous elimination of the triphenylbismuthonio group as bismuthine 5. Tropone 11c readily condenses with hydrazine hydrate to give a functionalized pyrazole 18.

DOI： 10.1039/A900751B

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEORG THIEME VERLAG  

Treatment of acenaphthenequinone with triphenylbismuthonium 2-oxoalkylides in THF at low temperature results in the C-insertion between two carbonyl functions, giving the corresponding 2-acyl-3-hydroxyphenalenones in good yield.

DOI： 10.1055/s-1999-3407

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DOI： 10.1021/ic981334g

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DOI： 10.1021/jo990690t

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DOI： 10.1021/om990252c

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DOI： 10.1021/om980914i

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Treatment of triarylbismuth difluorides with aryl- and alkenylboronic acids in the presence of BF3. OEt2 afforded tetraaryl- and alkenyltriarylbismuthonium tetrafluoroborates, respectively, while similar treatment of diphenyltellurinyl difluoride yielded the corresponding telluronium salts. The chirality at bismuth was observed for the first time from the H-1 NMR spectrum of an asymmetrical bismuthonium salt.

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The synthesis and properties of some new water-soluble non-ionic triarylbismuthanes are described. o-, m- and p-Tris(methoxymethoxyphenyl)bismuthanes 1a-c are prepared from BiCl3 and the corresponding organolithium or Grignard reagents. Oxidative chlorination of 1a-c with SO2Cl2 affords tris(methoxymethoxyphenyl)bismuth dichlorides 2a-c, which are deprotected by aqueous HCl to give tris(hydroxyphenyl)bismuth dichlorides 3a-c. Treatment of tris(3-hydroxyphenyl)bismuth dichloride 3b with NH2NH2 yields tris(3-hydroxyphenyl)bismuthane 5, which dissolves in dilute aqueous NaOH. N,N-Bis(2-tert-butyl-dimethylsiloxyethyl)benzenesulfonainide, prepared from benzenesulfonyl chloride and silyl-protected diethanolamine, is ortho-lithiated and reacted with 1/3 equiv. of BiCl3 to give Ar3Bi 9a {Ar = 2-[N,N-bis-(2-tert-butyldimethylsiloxyethyl)sulfamoyl]phenyl}. m-Phenylene-bridged Bi-2- and Bi-3-polybismuthanes 12 and 13 are prepared by the reaction between ortho-lithiated 9a and Ar2BiI 10, Desilylation of 9a, 12 and 13 by Bu4NF or p-TsOH . H2O in EtOH leads to the corresponding bismuthanepolyols 11, 14 and 15, The reaction between benzene-1,3-disulfonamide 16 bearing the silyl-protected bis(2-hydroxyethyl)amino side chains and 1/3 equiv. of BiCl3 affords tris{2,4-bis[N,N-bis(2-tert-butyldimethylsiloxyethyl)sulfamoyl]phenyl}bismuthane 17, which is deprotected by p-TsOH . H2O to yield tris{2,4-bis[N,N-bis(2-hydroxyethyl)sulfamoyl]phenyl}bismuthane 18, Compounds 11, 14 and 15 are only slightly soluble in water, but compound 18 is fairly soluble.

DOI： 10.1039/A803946A

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Triphenylbismuthonium 2-oxoalkylide 1, generated in situ from the corresponding onium salt 2 and base in THF at low temperatures, reacts with benzils 3 to give O-aroyl enolates of unsymmetrical 1,3-diketones 4 in moderate to good yields.

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Tp*ReO(H)Cl, TpRe(O)H(Cl), and Tp*ReO-(H)2 have been prepared by alkoxide-for-hydride metathesis using BH3·THF. The inflate derivative Tp*Re(O)H-(OTf) inserts olefins and is oxidized by oxygen-atom transfer reagents to give HOTf and Tp*ReO3, likely by a pathway involving hydride migration to an oxo ligand (Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate
triflate = OTf = OSO2CF3).

DOI： 10.1021/om980184e

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DOI： 10.1021/om9804531

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Successive treatment of triarylbismuth difluorides (1) with a Lewis acid, Me3SiCN, and aryltributylstannanes (2) in CH2Cl2 gives unsymmetrical tetraarylbismuthonium salts (3) in moderate to good yield. The migratory aptitude of an aryl ligand in [Ph3ArBi+][BF4 -] (3a, b) in the C-arylation of 2-naphthol is Ph&gt
p-Tol&gt
p-Ans.

DOI： 10.1246/cl.1998.127

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DOI： 10.1039/a801879k

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DOI： 10.1021/om980411c

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Several mixed triarylbismuthanes bearing an electron-withdrawing functionality, such as the nitro, carbonyl, or ester group, which are inaccessible by the conventional methods based on organometallic reagents such as Grignard and organolithium compounds, are synthesized in low to acceptable yields by the reaction of in situ generated sodium diarylbismuthide with iodoarenes or arenediazonium tetrafluoroborates.

DOI： 10.1021/om9701377

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Directed tris-ortholithiation of tris[2-(diethylaminosulfonyl)phenyl]bismuthane 1 with tert-butyllithium followed by treatment with 3 equiv. of bis[2-(diethylaminosulfonyl)-phenyl]bismuth iodide 2a gives a symmetrically branched Bi4-bismuthane 5a, which, on a similar treatment, is converted in a one-pot synthesis into a highly branched Bi10-bismuthane 6a.

DOI： 10.1039/a706338e

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A new general approach to a variety of unsymmetrical telluronium salts has been developed. Treatment of diaryltellurinyl difluorides 1 with silyl enol ethers 2 in the presence of BF3·OEt2 gave (2-oxoalkyl)diaryltelluronium tetrafluoroborates 3 in quantitative yield. When a siloxycyclopropane, an allylsilane, a benzylstannane, an alkenylstannane, an alkynylsilane, or an arylstannane was used in place of compound 2, the corresponding 3-oxoalkyl-, allyl-, benzyl-, alkenyl-, and alkynyldiaryltelluronium tetrafluoroborates as well as the unsymmetrically triarylated telluronium salt were obtained in good yields. The 125Te chemical shifts of these compounds span over the range δ 645-755 ppm, which were in accordance with the onium nature of the tellurium center. An X-ray structural analysis of 3a clearly showed that the central tellurium atom has a distorted-pyramidal structure with a weak coordinative interaction between the tellurium and carbonyl oxygen atoms. The telluronium salt [Ph2TeCH2CH2C(=O)Bu-t]+[BF 4]- easily transferred its alkyl moiety to a sulfinate anion to form the corresponding alkyl phenyl sulfone and diphenyl telluride, while the base-promoted reaction of [Ph2TeCH2C(=O)Ph]+[BF4]- with benzaldehyde afforded a chalcone and diphenyl telluroxide.

DOI： 10.1021/om960320k

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Treatment of triphenylbismuth difluoride with alkenyltrimethylsilanes 1 or trimethylsilyl cyanide-alkenyltrialkylstannanes 3 in the presence of boron trifluoride-diethyl ether gave the corresponding alkenyltriphenylbismuthonium tetrafluoroborates 2 in moderate to good yields, An X-ray crystallographic analysis of the salt 2e confirmed the distorted tetrahedral geometry of the central bismuth atom, When treated with a sulfinate 5 or the thiolate 11, the salts 2 readily transferred both the vinyl and phenyl moieties to these nucleophiles to afford the sulfones 7-10 or the sulfides 12, 13, respectively, In the presence of a palladium catalyst, the salt 2e underwent the Heck-type reaction with ethyl acrylate 17 to afford the dienoate 18 and cinnamate 19 in moderate yields, Action of KOBu(t) on the salt 2b yielded p-tolylacetylene 22, while a similar reaction with the salt 2e in the presence of the styrenes 23 gave the cyclopropanes 24, A Hammett study of the latter reaction has suggested a possible involvement of an alkylidenecarbene as the intermediate in these base-promoted reactions.

DOI： 10.1039/P19960001971

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Triarylbismuthanes bearing three different aryl groups, Ar1Ar2Ar3Bi (4), have been conveniently synthesized by the action of aryl Grignard reagent Ar3-MgBr on unsymmetrical diarylbismuth triflate-HMPA complexes Ar1Ar2BiOTf(HMPA)2 (8), which are readily accessible by the selective cleavage of triarylbismuthanes Ar12Ar2Bi (7
Ar1 is more fugacious than Ar2) with trimethylsilyl triflate in the presence of HMPA.

DOI： 10.1021/om9509709

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Triphenylbismuthonium 2-oxoalkylide 2, generated in situ from salt 1 in THF at low temperature, readily reacts with 1,2-dicarbonyl compounds 3 to give 2,3-diacyloxiranes 4 or 2-acyl-3-hydroxytropones 5 depending on the structure of the electrophiles involved.

DOI： 10.1039/cc9960002697

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This article is intended to describe recent progress in the chemistry of bismuthonium compounds, represented by onium salts, ylides, and imides, that have long been left untouched within the frame of heteroatom chemistry mainly because of limited access. However, the recent development of methodologies for the preparation of bismuthonium compounds has enabled us to unveil their properties as well as their chemistry. The article is comprised of three sections that mainly deal with: bismuthonium salts synthesized from triphenylbismuth difluoride and organo-silanes or -stannanes
stabilized and moderately stabilized bismuthonium ylides synthesized from triphenylbismuth(V) compounds and bismuthonium salts
and bismuthane imides prepared by oxidative imination of bismuthanes and by reaction between triphenylbismuth(V) dihalides and sulfonamides. Synthesis, X-ray structures, and typical reaction modes of these bismuthonium compounds are delineated in the order in which they appear.

DOI： 10.1246/bcsj.69.2673

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Reaction of triarylbismuth difluorides 1 with allyltrimethylsilane 2 in CH2Cl2 in the presence of BF3 . OEt(2) at low temperature generates allyltriarylbismuthonium compound 3 as a pale yellow solution, in which aromatic hydrocarbons and ethers, triphenylphosphine, dimethyl sulfide, p-toluenesulfinate, and thiophenol are all readily allylated to afford the corresponding allyl derivatives in moderate to good yields.

DOI： 10.1016/0040-4039(95)01600-7

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Treatment of triarylbismuth difluorides 2 with siloxycyclopropanes 3 in the presence of trimethylsilyl trifluoromethanesulfonate (triflate) or boron trifluoride-diethyl ether gave the corresponding triaryl(3-oxoalkyl)bismuthonium salts 4 as crystals, X-Ray crystallographic;analysis of the triflate 4a showed that the central bismuth atom has a distorted tetrahedral geometry with weak intramolecular coordination by the oxygen atoms of the carbonyl group and triflate anion, Whilst all onium salts 4 are thermally stable in a solid state, the triflate 4a slowly decomposed in chloroform to give triphenylbismuthane 6 and an ester 7 quantitatively, In nucleophilic solvents such as MeOH, DMSO and DMF, both triflate 4a and tetrafluoroborate 4d underwent decomposition in a complicated way to afford the bismuthane 6, 3-methoxypropanoyl compounds 8a,b, alpha,beta-unsaturated carbonyl compounds 9a,b, diphenylbismuth triflate 10a or tetrafluoroborate 10b and alkoxysulfonium salts 11a,b, The formate 12 was an additional product from 4d in DMF. The bismuthonium salt 4d reacted with dimethyl sulfide 13 and sodium benzenesulfinate 15 to afford the sulfonium salt 14 and the sulfonyl ketone 16, respectively, Reaction of the salt 4d with potassium halides 17 in DMF gave the enone 9b, formate 12 and halogeno ketone 18 in varying yields depending on the nucleophilic nature of the halogen anions employed. When treated with KOBu(t), the salt 4d underwent facile beta-elimination to yield the enone 9b. In all of these reactions, the triphenylbismuthane moiety behaved as a good leaving group.

DOI： 10.1039/P19950002543

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/jo00119a056

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Treatment of (2-oxoalkyl)triphenylbismuthonium tetrafluoroborates 3 with potassium tert-butoxide in tetrahydrofuran at -78 degrees C produced triphenylbismuthonium 2-oxoalkylides 4, which readily underwent epoxidation with the aldehydes 5 to give the alpha,beta-epoxy ketones 7 with high trans selectivity. The ylide 4a reacted with dimedone 11, the sulfonic acid 13, the thiol 15 and the isocyanate 17 to afford the corresponding ketones 12, 14, 16 and 19 in moderate to good yields. Reaction of the ylide 4c with the alpha,beta-unsaturated ketones 10 and 21 afforded the 1,2-dibenzoyl- and the 1,2,3-tribenzoyl- cyclopropanes 20 and 22, respectively, although the yields were low. In the presence of a catalytic amount of-nitrosobenzene 23, the ylide 4a suffered a unique decomposition to give the 2,2,7,7-tetramethyloct-4-ene,3,6-dione 24 in quantitative yield, while the reaction with the nitrile oxide 25 yielded the isoxazoline 26. In all of these reactions, triphenylbismuthane 6 was the additional major product.

DOI： 10.1039/P19940002703

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Reaction of triarylbismuthines 1 with iodosylbenzene in dichloromethane under ultrasonic irradiation leads to the generation of triarylbismuthine oxides 2 as a bright yellow solution, in which activated alcohols are easily oxidized to carbonyl compounds, triphenylphosphine is converted into oxide and hydrazobenzene is rapidly dehydrogenated to azobenzene. Triphenylstibine 8 is similarly oxidized to give stibine oxide 9, which lacks the corresponding oxidizing ability.

DOI： 10.1016/0040-4039(94)88281-9

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Treatment of triarylbismuth difluorides 1 with silyl enol ethers 2 in the presence of boron trifluoride-diethyl ether or trimethylsilyl trifluoromethanesulfonate (triflate) gave (2-oxoalkyl)triarylbismuthonium tetrafluoroborates. 3 and triflates 4 in good yields. A similar reaction of the difluorides 1 with hexamethyldisiloxane in the presence of the latter acid reagent led to the formation of oxybis(triarylbismuth) ditriflates 5. X-Ray cyrstallographic analyses of compounds 3a, 4a and 5a showed that the first two onium salts have a distorted tetrahedral geometry and the last. a mu-oxo type compound, has a distorted trigonal bipyramidal geometry around the bismuth centre. The stability of these bismuthonium salts may reasonably be attributed to the intramolecular coordinative interaction between the bismuth and oxygen atoms and also low nucleophilicity of the counter ions employed. The bismuthonium salt 3f readily underwent onium exchange with the phosphine 6 and the sulfide 9 to afford the corresponding phosphonium and sulfonium salts 7 and 10. The salts 3 and 4 also underwent coupling with a variety of nucleophiles such as the enolate 11, piperidine 13, the phenoxides 15, the thiolates 17, the sulfinate 19 and the halides 21 to afford the corresponding alpha-substituted ketones 12, 14, 16, 18, 20 and 22 in moderate to good yields, together with a good recovery of triphenylbismuthine 8.

DOI： 10.1039/P19940001739

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Chiral chlorobismuthines 3 stabilized by intramolecular coordination of an NN-dimethylamino group have been synthesized by the selective fluorodearylation of the bismuthines 1 with boron trifluoride-diethyl ether, followed by halogen exchange of the resulting fluorobismuthines 2 with brine. An X-ray crystallographic structure analysis of 3b revealed that the bismuth centre has a distorted pseudotrigonal bipyramidal structure through the formation of a hypervalent 3-centre 4-electron bond with the chlorine and nitrogen atoms at apical positions. H-1 NMR spectra of compounds 3 in CDCl3 at room temperature reflected their fixed conformation in the solid state. Chiral chlorobismuthines 7a and 7b were obtained in a similar manner starting from optically pure (R)-N,N-dimethyl-1-phenylethylamine as a mixture of two diastereoisomers (77:23 and 78:22, respectively), the isomeric ratios of which were not influenced by the equatorial aryl groups present. Variable-temperature dynamic H-1 NMR spectra of the diastereoisomeric mixture of 7a provided important information about its behaviour in solution; in [H-2(8)]toluene dynamic but reversible dissociation of intramolecular Bi-N coordination was observed only at elevated temperatures, while in [H-2(6)]-DMSO it occurred quite easily below room temperature, leading to the inversion of configuration at the chiral bismuth centre.

DOI： 10.1039/P19930002969

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEORG THIEME VERLAG  

On treatment with an excess of sodium azide in the presence of titanium(IV) chloride in boiling acetonitrile, both aliphatic and aromatic ketones are smoothly converted to 1,5-disubstituted 1H-tetrazoles in high yields.

DOI： 10.1055/s-1993-26027

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Treatment of triarylbismuth difluorides 1 with silyl enol ethers 2 in the presence of BF3.OEt(2) gives (2-oxoalkyl)triarylbismuthonium tetrafluoroborates 3 as a stable crystalline solid, the bismuth centre of which has been found by X-ray analysis to possess a tetragonal geometry. The 2-oxoalkyl moiety of compound 3 couples with enolates and thiolates to afford the corresponding triketones 4 and alpha-thioketones 6, respectively.

DOI： 10.1016/S0040-4039(00)61358-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Oxidation of triphenylbismuthine 1 with ozone in toluene at -78-degrees-C gave, unexpectedly, a high yield of triphenylbismuth diformate 3, which was also obtainable as a minor product by a similar oxidation in ethyl acetate and acetone. An X-ray crystallographic study revealed that compound 3 has C2 symmetry, the geometry around the bismuth atom being best described as a distorted trigonal bipyramid as a result of strong intramolecular interaction between the bismuth and carbonyl oxygen atoms. Treatment of compound 3 with aqueous sodium acetate or halides readily converted it into the corresponding triphenylbismuth diacetate 5 or dihalides 7-9.

DOI： 10.1039/P19930002411

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Irradiation of a triarylbismuth diazide in benzene in the presence of alkynes results in the transfer of one of the azido ligands to the triple bond, leading to N-unsubstituted 1,2,3-triazoles in fair to moderate yields.

DOI： 10.1016/S0040-4039(00)77490-9

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Chemical Society of Japan  

Bismuth trichloride reacts smoothly with mesityl- and 2,4,6-triisopropylphenylmagnesium bromides in boiling tetrahydrofuran to form the corresponding triarylbismuthines in good yields, while a similar reaction with 2,4,6-triisopropylphenylmagnesium bromide halts at diarylation stage, giving chlorobis(2,4,6-triisopropylphenyl)bismuthine as the sole product. Several crowded alkyl-, alkenyl-, and alkyn-yldiarylbismuthines have been prepared from the above diarychlorobismuthine through the reaction with an appropriate organolithium reagent.

DOI： 10.1246/bcsj.65.3504

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Chemical Society of Japan  

DOI： 10.1246/cl.1991.105

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

The mechanism of the Grignard reactions of substituted benzophenones with two kinds of alkyl Grignard reagent, n‐C3H7MgBr, and i‐C3H7MgBr, was investigated. In these reactions, both addition and reduction products were also generated. Based on the results of product analysis and stopped‐flow, ESR and association measurements, it was confirmed that the product distribution was governed by several factors: the oxidizing ability of benzophenones, the association ability of Grignard reagents and the structure of alkyl groups of Grignard reagents. In particular, the strength of CMg and β‐CH bonds of Grignard reagents could strongly affect the product distribution. Copyright © 1991 John Wiley &amp
Sons Ltd.

DOI： 10.1002/poc.610040806

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Chemical Society of Japan  

Although the photochemically induced reaction of benzil with allyltrimethylstannane in benzene afforded α-allylbenzoin as a major product, benzil did not react thermally with the same reagent. An ESR observation disclosed that the benzil anion radical ion-paired upon contact with trimethylstannyl cation (BSnMe3) was generated during irradiation. Its structure was confirmed by the detection of satellite signals arising from tin isotopes. Moreover, a triplet radical pair was also observed during the photolysis of a solid solution containing benzil and allylstannane at 77 K. This reaction proceeded via a single electron transfer from allylstannane to photoexcited benzil, followed by a cleavage of the C-Sn bond of the allyltin cation radical. Ultimately, a radical pair composed of BSnMe3 and the allyl radical was formed and their coupling gave α-allylbenzoin as an isolated product.

DOI： 10.1246/bcsj.63.2218

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Chemical Society of Japan  

Thermal reactions of acylquinones with allylstannanes in benzene afforded several kinds of product after column chromatography on silica gel; acyl allyl quinones, acyl allyl epoxy quinones, cyclopentanoid compounds including stannyl moiety, allyl hydroxy quinones, acyl hydroquinones, and acyl allyl hydroquinones. The main product comprises cyclopentanoid compounds, which are novel [2+3] cyclo adducts with 1,2-migration of trialkylstannyl moiety. Spectroscopic examinations (<SUP>1</SUP>H NMR and Vis-UV) enabled us to confirm the reaction pathways that four types of precursors were initially generated via polarized tight pair and inverted to isolated products during purification by column chromatography. Similar reactions in acetonitrile showed a remarkable difference in the reactivity, that is, acyl allyl quinones and the corresponding hydroquinones are obtained, but the [2+3] cyclo adducts are not produced at all. From <SUP>1</SUP>H NMR examination, it was confirmed that three types of precursor are generated via solvent separated ion pairs at the initial stage. The rather strong reactivity of acylquinones towards allylstannanes will be due to electron withdrawing ability of acyl group.

DOI： 10.1246/bcsj.62.3877

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Language：English   Publishing type：Research paper (scientific journal)  

Allylstannanes recently attract much interest in the field of organic synthesis and photochemistry because of their remarked reactivities toward electrophiles. In the photochemical reactions of some electron acceptable substrates with allylstannanes, photo-induced single electron transfer mechanism has been proposed mainly based on the product analyses. However, few attempts to clarify the mechanism by detecting directly the reactive intermediates have been made so far. We have applied ESR technique to the photochemical and thermal reactions of quinones with allylstannanes. During irradiation, semiquinone radical combined with trialkylstannyl moiety and allyl radical were observed simultaneously in the case of p-quinones. No radical was detected in the dark. On the other hand, in the case of 9,10-phenanthraquinone, intense signal of semiquinone radical coordinated with trialkylstannyl moiety was observed not only during irradiation but also in the dark. It is doubtless, in the latter case, that ability of the two neighboring carbonyi oxygens to coordinate stannyl moiety is the most important factor for inducing the thermal electron transfer. The results obtained by ESR disclosed us the features of reactive paramagnetic intermediates and enabled us to make sure the mechanism of these allylations, 1) photo-induced or thermal single electron transfer occurred from allylstannane to quinone. 2) Cleavage of the cation radical by assist of the quinone anion radical generated radical pair. 3) Combination between semi-quinone radical combined with stannyl moiety and allyl radical afforded allylated products. Evidently, regioselectivity of allylation was dependent on the spin densities of radical intermediates. © 1989, The Chemical Society of Japan. All rights reserved.

DOI： 10.1246/nikkashi.1989.1351

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Language：Japanese   Publisher：The Society of Physical Organic Chemistry, Japan  

Core-modified porphyrins are one of the porphyrin analogues, in which at least one core nitrogen atom is replaced by another atom. Although the chemistry of core-modified porphyrins has attracted much attention, phosphorous-containing porphyrins, namely &quot;phosphaporphyrins&quot;, have not been prepared. Here we report the first synthesis of phosphaporphyrin and its aromaticity as well as optical and electrochemical properties. A phosphaporphyrin was synthesized via acid-promoted condensation of phosphatripyrrane with 2,5-bis[hydroxy(phenyl)methyl]thiophene. The NMR and UV-vis absorption spectra, and CV has revealed that the phosphaporphyrin possesses a considerable aromaticity and a relatively narrow HOMO-LUMO energy gap.

DOI： 10.11494/kisoyuki.18.0.17.0

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Language：Japanese   Publisher：技術情報協会  

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It is known that phosphole has a high electron-accepting ability. To construct chemically and thermally stable pi-conjugated phospholes, we designed three types of naphthalene-fused phosphole derivatives, and succeeded in preparing the desired compounds based on a titanacycle methodology. The structure-property relationship will be presented.

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Three types of bithiophene-fused benzo[&lt;I&gt;c&lt;/I&gt;]phospholes were synthesized via TiII-mediated intramolecular cyclization of dialkynylated bithiophene derivatives. The X-ray structures, theoretical calculations, UV-vis absorption and fluorescence spectra, and electrochemical measurements have revealed that the structural, optical, and electrochemical properties of the bithiophene-fused benzo[&lt;I&gt;c&lt;/I&gt;]phospholes vary considerably depending on the pi-conjugation modes at the bithiophene subunits. The appropriately ring-annulated sigma3-P derivatives were found to emit fluorescence in the orange-to-red region, and the P-oxo derivatives proved to undergo reversible one-electron reduction in cyclic voltammetry

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