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

The synthesis of robust high-spin carbon radicals is an important topic in organic chemistry. Toward this end, several porphyrin-stabilized radicals have been systematically explored. A singly naphthalene-fused porphyrin radical was synthesized by a reaction sequence consisting of a Suzuki–Miyaura coupling of β-borylated porphyrin with 2-bromobenzaldehyde, addition of mesityl Grignard reagent, intramolecular Friedel–Crafts alkylation, and final oxidation with DDQ or tBuOK/O2. This strategy was also used to synthesize doubly naphthalene-fused porphyrins and syn- and anti-fused-anthracene-bridged porphyrin dimers. While singly naphthalene-fused porphyrin radical has been shown to be a stable monoradical, doubly naphthalene-fused porphyrins and anti-fused-anthracene-bridged porphyrin dimers have been shown to be closed-shell molecules. Finally, the syn-dimer was characterized as a surprisingly stable radical (t1/2=28 days under ambient air and at 80 °C) that is storable for more than several months, despite its high-spin triplet ground-state carbon diradical.

DOI： 10.1002/anie.202015356

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/anie.202015356

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Near-infrared two-photon (NIR-2P) uncaging reactions are useful for precise investigations of the roles of biologically active compounds in various phenomena. In this study, we synthesized new NIR-2P-responsive chromophores with terphenyl backbones featuring an ethylene glycol tetraacetic acid (EGTA) unit as a Ca -selective chelator. The photolabile Ca chelators were synthesized in high yields (83 % for 1a, 45 % for 1b) from commercially available starting materials. One- and two-photon photochemical excitations of the synthesized terphenyl derivatives featuring two different electron-donating groups (dimethylamino (NMe ) and methoxyl (OMe)), which were thermally stable at least 36 h at 37 C in HEPES buffer (pH 7.4), were conducted to clarify the substituent effect on the photophysical and photochemical properties. The NMe group, which is a stronger electron-donating group, has led to a higher two-photon cross-section (σ = 75 GM at 780 nm) compared to the OMe group (σ = 9 GM at 720 nm) in a pH = 7.4 HEPES buffer solution, although the molar extinction coefficient (ε) of the NMe -substituted one (ε = 10,371 at λ =363 nm) was lower than that of the OMe-derivative (ε = 14,351 at λ = 344 nm). The quantum yield (Φ = 0.04) for the decomposition of the NMe -substituted caged compound was lower than that for the OMe-substituted caged compound (Φ = 0.40). One and two-photon uncaging efficiency values of the OMe substituted compound, ε × Φ = 5740 and σ × Φ = 3.6, were higher than those of the NMe -substituted compound, 415 and 3.0, respectively. Laser flash photolysis experiments clarified the decay rate constants (2.5 × 10 and 1.1 × 10 s ) of aci-nitro intermediates formed during the uncaging process. A concentration jump of Ca was confirmed in the photolysis of caged calcium compounds newly synthesized in this study, indicating the terphenyl derivatives can be also utilized in physiological experiments. The corresponding acetoxymethyl esters were also prepared for physiological studies. 2+ 2+ 6 2 −1 2+ 2 2 2 2 2 max max 2 2 2

DOI： 10.1016/j.jphotochem.2021.113154

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This paper presents a novel series of chemically stable and redox-switchable 20π, 19π, and 18π5,10,15,20-tetraaryl-5,15-diazaporphyrinoids (TADAPs) that have two alkyl-chain straps above and below the diazaporphyrin ring. Three types of doubly strapped TADAPs were prepared as nickel(II) complexes using meso-N-(2,6-dihydroxyphenyl)-substituted TADAP and the corresponding aliphatic diacids as precursors. Theoretical calculations revealed that regardless of their oxidation states, all strapped TADAPs had essentially flat π-planes. It was found that the alkyl-chain straps slightly affected the optical and electrochemical properties of the DAP rings, particularly in the oxidized forms. 1H NMR spectroscopy was used to evaluate the antiaromatic character of the 20πTADAPs and the aromatic character of the 18πTADAP dications, and it was observed that they displayed paratropic and diatropic ring-current effects, respectively, on the chemical shifts of methylene protons in the spatially separated alkyl chains. The degree of shielding and deshielding depended on the position of the methylene units; it decreased with increase in separation from the π-plane and central axis of the porphyrin ring. The NMR experiments also revealed that the degree of the diatropic ring currents was clearly related to the π-electron density of the porphyrin ring; the ring-current effects decreased as the charge increased from 0 to +2. These findings are also qualitatively supported by the nucleus-independent chemical shifts.

DOI： 10.1021/acs.joc.0c02433

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

Orientational control of functional molecules is essential to create complex functionalities as seen in nature; however, such artificial systems have remained challenge. Herein, we have succeeded in controlling rotational isomerism of mu-oxo silicon phthalocyanine (SiPc) oligomers to achieve an external-stimuli-responsive orientational ordering using intermolecular interactions of tetrathiafulvalene (TTF). In this system, three modes of orientations, free rotation, eclipsed conformation, and staggered conformation, were interconverted in response to the oxidation states of TTF, which varied interactions from association due to formation of mixed-valence TTF dimer to dissociation due to electrostatic repulsion between TTF dications. Furthermore, a stable performance of oligomers as a cathode material in a Li-ion battery proved that the one-dimensionally stacked, rotatable structure of SiPc oligomers is useful to control the orientation of functional molecules toward molecular electronics.

DOI： 10.1002/anie.202011025

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

Isolation and structural characterization of hypervalent electron-rich pentacoordinate nitrogen species have not been achieved despite continuous attempts for over a century. Herein we report the first synthesis and isolation of air stable hypervalent electron-rich pentacoordinate nitrogen cationic radical (11-N-5) species from oxidation of their corresponding neutral (12-N-5) species. In the cationic radical species, the nitrogen centers adopt a trigonal bipyramidal geometry featuring a 3-center-5-electron hypervalent attractive interaction. The combination of single crystal X-ray diffraction analysis and computational studies revealed weak N-O interactions between the central nitrogen cation and oxygen atoms. This successful design strategy and isolation of air-stable pentacoordinate hypervalent nitrogen species allow further investigations on reactivity and properties resulting from these unusually weakly coordinating interactions in nitrogen compounds.

DOI： 10.1039/d0sc00002g

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

2,18-Bis(dicyanomethyl)-substituted Ni-II porphyrin 8 and Zn-II porphyrin 11 were prepared and subjected to oxidation with PbO2 in CH2Cl2 at 298 K to give cyclophane-type chlorin dimers (9)(2) and (12)(2) as a consequence of double recombination of biradicals 9 and 12, respectively. Dimer (9)(2) takes a syn-conformation of two distorted Ni-II chlorins but (12)(2) takes an anti-conformation of relatively planar Zn-II chlorins. At 298 K, dimer (9)(2) is stable and its H-1 NMR spectrum is sharp but becomes broad at high temperature, while the H-1 NMR spectrum of (12)(2) is considerably broad even at 298 K but becomes sharper at low temperature. These results indicate that the chlorin dimers dissociate to radical species, but the activation barrier of the dissociation of (12)(2) is much less than that of (9)(2). The involvement of diradicals in dynamic covalent chemistry has been suggested by thermal scrambling of hetero dimer (16)(2) to give homo dimers (9)(2) and (15)(2).

DOI： 10.1002/anie.201914480

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCI PUBL CO INC  

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 pi, 19 pi, and 18 pi oxidation states of the DAP ring in the TADAP-TAs were reversibly interconvertible by redox reactions. NMR spectroscopy of the 20 pi and 18 pi Ni-TADAP-TAs revealed their antiaromatic and aromatic characters, respectively, whereas electron paramagnetic resonance spectroscopy of the 19 pi 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 pi-electron system. Notably, all the 18 pi 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 pi/19 pi and 19 pi/18 pi 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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(Porphyrinyl)dicyanomethyl radicals were produced by oxidation of dicyanomethyl-substituted porphyrins with PbO2. These radicals constitute a rare example displaying stable radical versus dynamic covalent chemistry (DCC) depending upon the substitution position of the dicyanomethyl radical. meso-Dicyanomethyl-substituted radicals exist as stable monomeric species and do not undergo any dimerization processes either in the solid state or in solution. In contrast, β-dicyanomethyl-substituted radicals are isolated as σ-dimers that are stable in the solid-state but display reversible σ-dimerization behavior in solution; monomeric radical species exist predominantly at high temperatures, while σ-dimerization is favoured at low temperatures. This dynamic behaviour has been confirmed by variable-temperature 1H NMR, UV-vis and EPR measurements. The structures of the stable radical and σ-dimer have been revealed by single-crystal X-ray diffraction analysis. The observed different reactivities of the two (porphyrinyl)dicyanomethyl radicals have been rationalized in terms of their spin delocalization behaviours.

DOI： 10.1039/c9sc01631g

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

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

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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DOI： 10.1002/anie.201810200

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Publisher：Wiley  

DOI： 10.1002/ange.201810200

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DOI： 10.1038/s42004-018-0048-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Endohedral metallofullerenes have been extensively studied since the first experimental observation of La@C-60 in a laser-vaporized supersonic beam in 1985. However, most of these studies have focused on metallofullerenes larger than C-60 such as (metal)@C-82, and there are no reported purified C-60-based monomeric metallofullerenes, except for [Li@C-60] +(SbCl6)-salt. Pure (metal)@C-60 compounds have not been obtained because of their extremely high chemical reactivity. One route to their stabilization is through chemical functionalization. Here we report the isolation, structural determination and electromagnetic properties of functionalized crystalline C-60-based metallofullerenes Gd@C-60(CF3)(5) and La@C-60(CF3)(5). Synchrotron X-ray single-crystal diffraction reveals that La and Gd atoms are indeed encapsulated in the I-h-C-60 fullerene. The HOMO-LUMO gaps of Gd@C-60 and La@C-60 are significantly widened by an order of magnitude with addition of CF3 groups. Magnetic measurements show the presence of a weak antiferromagnetic coupling in Gd@C-60(CF3)(3) crystals at low temperatures.

DOI： 10.1038/s41467-018-05496-8

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© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 5,15-Dioxaporphyrin was synthesized for the first time by a nucleophilic aromatic substitution reaction of a nickel bis(α,α′-dibromodipyrrin) complex with benzaldoxime, followed by an intramolecular annulation of the α-hydroxy-substituted intermediate. This unprecedented molecule is a 20π-electron antiaromatic system, in terms of Hückel's rule of aromaticity, because lone pair electrons of oxygen atoms are incorporated into the 18π-electron conjugated system of the porphyrin. A theoretical analysis based on the gauge-including magnetically induced current method confirmed its antiaromaticity and a dominant inner ring pathway for the ring current. The unique reactivity of 5,15-dioxaporphyrin forming a β,β-linked dimer upon oxidation was also revealed.

DOI： 10.1002/anie.201804648

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

DOI： 10.1002/anie.201804644

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCI PUBL CO INC  

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

Control of open-shell character of meso-meso linked porphyrin meso-oxy radical dimers has been demonstrated by core metalation. Namely, NiII-porphyrin dimer 6Ni exhibits a clear 1H NMR spectrum and a distorted but rather coplanar quinonoidal structure consisting of two ruffled porphyrin rings, in accordance with the previous report. Freebase dimer 6H2 shows a similar quinonoidal structure in the solid state but displays slightly broader and temperature-dependent 1H NMR spectra, indicating a partial diradical character in solution that increases at high temperature. In sharp contrast, bis-imidazole-coordinated ZnII-porphyrin dimer 6ZnIm2 exhibits a perpendicular structure consisting of two planar ZnII-porphyrins and has been characterized as a distinct open-shell diradical on the basis of its non-observable 1H NMR signals, a clear ESR signal, and a characteristic absorption spectrum reaching about 1700 nm. Despite the distinct diradical character, 6ZnIm2 is an extremely stable molecule.

DOI： 10.1002/chem.201705769

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

Stable helical radicals are promising multi-functional molecules in light of intriguing magnetic and chiroptical properties. Attempts were made to extend diphenylmethyl-fused NiII porphyrin radical to helical system as the first air-stable organic neutral helical radicals. Intramolecular Pd-catalyzed twofold C−H arylation of methyl- or methoxy-introduced meso-diphenylmethyl NiII porphyrins gave a mixture of the target and rearranged radicals. Oxidative fusion reaction of meso-(bis(1-naphthyl)methyl) NiII porphyrins provided doubly fused NiII porphyrin radicals. One of the helical radicals was separated into enantiomers that showed mirror-image circular dichroism (CD) spectra up to 1300 nm. The helical dinaphthylmethyl-fused NiII porphyrin radical displayed solid-state magnetic property mostly arising from monomeric radicals, different from the parent diphenylmethyl-fused NiII porphyrin radical that showed antiferromagnetic coupling due to π-stacked pairing.

DOI： 10.1002/chem.201705291

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

Cofacial assemblies of metalloporphyrinoids represent a fascinating platform for the fabrication of novel functional molecular assemblies based on π-π, d-d, and d-π interactions between components. In this paper, we present a novel synthetic strategy for the programmable arrangement of different metal ions inside a cofacially stacked trimer of porphyrinoids. A combination of two different assemblies was utilized for our purpose: a tetracationic fourfold rotaxane heterodimer between a porphyrin with four alkylammonium chains and a phthalocyanine bearing four peripheral crown ethers, and a stacked assembly between the fourfold rotaxane heterodimer and an additional tetraanionic porphyrin. Three metal ions, namely Cu(ii), Ag(ii), and Au(iii), were arranged inside the cofacially stacked assembly of three porphyrinoids. Moreover, paramagnetic Cu(ii) ions were arranged inside a cofacially stacked heterotrimer of porphyrinoids and were precisely programmed, affording the desired spin-spin communications as readable information. These results indicated that the developed strategy is effective for arranging various metal ions in cofacially stacked assemblies of porphyrinoids toward the creation of molecular tags or bar codes.

DOI： 10.1039/c8dt01334a

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© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A contracted doubly N-confused dioxohexaphyrin(1.1.1.1.1.0) complex consisting of two paramagnetic copper metals and open-shell π-radical ligand was synthesized as a new multi-heterospin motif. X-ray spectroscopy supported the divalent character of the inner copper centers, and electron paramagnetic resonance and magnetometric studies suggested the presence of unpaired d electrons strongly antiferromagnetically coupled with π-radicals delocalized on the macrocycle. The 25 π non-innocent dioxohexaphyrin ligand allowed the facile interconversion between antiaromatic 24 π and aromatic 26 π species, respectively, upon redox reactions.

DOI： 10.1002/chem.201704321

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

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

To explore stable organic diradicaloids, meso-thie-nylquinonoid- substituted porphyrins Pn and hexaphyrins Hn, where "n" denotes the number of thienyl units in the meso-substituents, were synthesized. P0 was identified as a closed-shell quinonoid, whereas P1 was shown to possess significant diradical character with diradical character index (y) of 0.99 and quite small singlet-triplet energy gap (Delta ES-T) of -0.13 kcal mol(-1). P1 was certainly stable, allowing its isolation, but decomposed gradually in solution. In the hexaphyrin series, it was shown that H0 and H1 were closed-shell quinonoids, but H2 was a highly stable diradicaloid with y=0.85 and Delta ES-T of -3.72 kcal mol(-1). The high stability of H2 was ascribed to effective spin delocalization over the entire conjugated network. Characteristically, H2 displays an intense absorption band in NIR region at lambda(max)= 1175 nm with molar absorption coefficient (is an element of) of 8.81 x 10(4) mol(-1) Lcm(-1), a narrow HOMOL-UMO gap of 0.69 eV, and nine reversible redox potential waves.

DOI： 10.1002/chem.201701355

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

Most aminyl radicals studied so far are resonance-stabilized by neighboring heteroatoms, and those without such stabilization are usually short-lived. We report herein that subporphyrin meso-2,4,6-trichlorophenylaminyl radicals and a bis(5-subporphyrinyl)aminyl radical are fairly stable under ambient conditions without such stabilization. The subporphyrin meso-2,4,6-trichlorophenylaminyl radical crystal structure displays a characteristically short C-meso-N bond and a perpendicular arrangement of the meso-arylamino group. The stabilities of these radicals have been ascribed to extensive spin delocalization over the subporphyrin p-electronic network as well as steric protection around the aminyl radical center.

DOI： 10.1002/anie.201703097

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

To investigate the intrinsic reactivity of atomic nitrogen, which had previously been accomplished only by examining its decay in the gas phase using special equipment, a nitrogen atom was inserted into a series of molecule-encapsulating C-60 and C-70 fullerenes. Among the studied endofullerenes, H-2@C-70 was able to encapsulate an additional nitrogen atom within the fullerene cage under radiofrequency plasma conditions. The product was analyzed by ESR spectroscopy and mass spectrometry in solution, which revealed that the nitrogen atom with a quartet ground state does not react but weakly interact with the H-2 molecule, thus demonstrating the utility of such fullerenes as "nanoflasks".

DOI： 10.1002/anie.201701158

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

10,15,20-Tris(pentafluorophenyl) substituted Ni-II-porphyrin meso oxy radical bearing two coordinating pyridines was synthesized as a stable radical with a quartet ground state (S = 3/2). X-ray structural analysis revealed that the Ni-II-porphyrin moiety is fairly planar and the Ni-N bond lengths are considerably longer, indicating the highspin state of the Ni-II center. The radical exhibited a quartet ground state, indicating the ferromagnetic interaction between the high spin NiII center (S = 1) and the porphyrin meso oxy radical (S = 1/2).

DOI： 10.1002/chem.201701354

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

A caged carboxylic acid with a novel two-photon (TP)-responsive donor-pi-donor coumarin backbone with a quadrupolar nature was designed and synthesized in this study. The newly synthesized coumarin derivative showed a strong one-photon (OP) absorption band (epsilon approximate to 29000 cm(-1) M-1) in the visible region (>similar to 400 nm). Time-dependent density functional theory calculations predicted a sizable TP absorption cross-section with a maximum at similar to 650 nm significantly lager than that related to the OP absorption band. This is confirmed experimentally using TP excited fluorescence in the fs regime that leads to TP absorption cross-section of 18 and 5.6 GM at 680 and 760 nm, respectively. The OP photolysis (400 nm) and near-infrared-TP photolysis (750 nm) of the caged benzoic acid resulted in a clean formation of benzoic acid and an aldehyde.

DOI： 10.1021/acs.orglett.7b00957

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

New allene compounds bearing 1,8-diphenoxy or bis(3,5-di-tert-butylphenyl) oxyacridene (diaryloxyacridene) moieties were synthesized. These compounds were more easily oxidized than Cl-substituted compounds. The allene compounds were oxidized to generate thermally stable triplet carbenes. Electron spin resonance and electron spin transient nutation spectra of the oxidation reaction products suggested the generation of triplet species; however, the main isolated product from the 1,8-diphenoxy allene was a cyclized compound that was characterized by X-ray analysis. The product derived from diaryloxy allene was also characterized by X-ray analysis as a singlet species, which included a vinyl cation stabilized by a neighboring O(3,5-di-tert-butylphenyl) group. This singlet species was stable even at room temperature and did not show any electron spin resonance signals in solution, indicating that the triplet species was not in equilibrium with the singlet. Copyright (C) 2016 John Wiley & Sons, Ltd.

DOI： 10.1002/poc.3665

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

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

Oxidative fusion reactions of meso-phenoxazino Ni(II) porphyrin were found to be temperature dependent, giving rise to either a doubly phenylene-fused product at room temperature or a singly phenoxazine-fused product at 70 degrees C. The latter was further oxidized to a doubly phenoxazine-fused Ni(II) porphyrin, which was subsequently converted to the corresponding free base porphyrin and Zn(II) porphyrin. Compared to previously reported diphenylamine-fused porphyrins that displayed a molecular twist, doubly phenoxazine-fused porphyrins exhibited distinctly different properties owing to their highly planar structures, such as larger fluorescence quantum yields, formation of an offset face-to-face dimer both in solution and the solid state, and the generation of a mixed-valence p-radical cation dimer upon electrochemical oxidation. One-electron oxidation of the phenoxazine-fused Ni(II) porphyrin with Magic Blue gave the corresponding radical cation, which was certainly stable and could be isolated by separation over a silica gel column but slowly chlorinated at the reactive beta-positions in the solid state. This finding led to us to examine beta, beta'-dichlorinated phenoxazine-fused and diphenylamine-fused Ni(II) porphyrins, which, upon treatment with Magic Blue, provided remarkably stable radical cations to an unprecedented level. It is actually possible to purify these radical cations by silica gel chromatography, and they can be stored for over 6 months without any sign of deterioration. Moreover, they exhibited no degradation even after the CH2Cl2 solution was washed with water. However, subtle structural differences (planar versus partly twisted) led to different crystal packing structures and solid-state magnetic properties.

DOI： 10.1039/c6sc02721k

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In spite of significant advances in redox-active porphyrin-based materials and catalysts, little attention has been paid to 20π and 19π 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 20π, 19π, and 18π 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 π-systems were assessed by using various spectroscopic measurements and density functional theory calculations. The aromaticity and π-π* electronic transition energies of the TADAPs varied considerably, and were shown to be dependent on the oxidation states of the π-systems. In contrast to the isoelectronic 5,10,15,20-tetraarylporphyrin derivatives, the 20π and 19π TADAPs were chemically stable under air. In particular, the 19π TADAP radical cations were extremely stable towards dioxygen, moisture, and silica gel. This reflected the low-lying singly occupied molecular orbitals of their π-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 19π/20π redox cycle.

DOI： 10.1002/chem.201703664

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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 π-skeletons of the metallodiazaporphyrin dimers.

DOI： 10.1002/asia.201700204

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

Novel pi-extended coumarin-based chromophores were designed with two-photon absorption (TPA) character in the near-TR. region. Caged benzoates with a TP-responsive chromophore were synthesized, and their TP-uncaging reactions were conducted under near-IR light. The 6,7-dimethoxy-substituted derivative had a high TPA cross-section of 69 GM at 740 nm. The 7-methoxy-substituted derivative showed a high TPA uncaging efficiency with a TPA efficiency of 3.4 GM at 710 nm.

DOI： 10.1246/cl.160586

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

Among biologically active compounds, calcium ions (Ca2+) are one of the most important species in cell physiological functions. Development of new calcium chelators with two-photon absorption (TPA) properties is a state-of-the-art challenge for chemists. In this study, we report the first and efficient synthesis of 5-bromo-2-nitrobenzyl-substituted ethylene glycol tetraacetic acid (EGTA) as a platform for a new generation of calcium chelators with TPA properties in the near-infrared region. New calcium chelators with high TPA properties, that is, a two-photon (TP) fragmentation efficiency of δu = 20.7 GM at 740 nm for 2-(4-nitrophenyl)benzofuran (NPBF)-substituted EGTA (NPBF-EGTA, Kd = 272 nM) and δu = 7.8 GM at 800 nm for 4-amino-4′-nitro-1,1′-biphenyl (BP)-substituted EGTA (BP-EGTA, Kd = 440 nM) derivatives, were synthesized using Suzuki-Miyaura coupling reactions of the bromide with benzofuran-2-boronic acid and 4-(dimethylamino)phenyl boronic acid, respectively. The corresponding acetoxymethyl (AM) esters were prepared and successfully applied to the Ca2+-uncaging reaction triggered by TP photolysis in vivo.

DOI： 10.1021/acsomega.6b00119

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

The direct fusion of a diphenylmethane segment to a Ni-II 5,10,15-triarylporphyrin with three linkages furnished an air-and moisture-stable neutral radical through unexpected and spontaneous oxidation. This radical was demetalated by treatment with H2SO4 and CF3CO2H to provide the corresponding free-base radical. These porphyrin radicals are very stable owing to spin delocalization and have been fully characterized through UV/Vis/NIR absorption spectroscopy, X-ray crystallographic analysis, magnetic susceptibility measurements, electrochemical studies, laser-based ultrafast spectroscopic studies, and theoretical calculations. They were chemically oxidized and reduced to the corresponding cation and anion but did not react with hydrogen-atom donors.

DOI： 10.1002/anie.201602683

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Treatment of meso-chlorosubporphyrin with controlled equivalents of Na(2)S9H(2)O in DMF led to the formation of either meso-to-meso sulfide (S)-bridged dimer 4 or disulfide (SS)-bridged subporphyrin dimer 6. S-bridged dimer 4 displayed a split Soret-like band and a large Stokes shift and became a fully delocalized one-quantum system in the S-1 state, as indicated by femtosecond transient absorption anisotropy measurements and theoretical calculations. Contrastingly, SS-bridged dimer 6 showed a broad but nonsplit Soret-like band, no fluorescence, and very fast S-1 decay with a lifetime of 4 ps, which indicated the presence of a rapid decay channel.

DOI： 10.1002/ejoc.201600285

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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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Using a newly prepared tridentate ligand, we isolated hypervalent sulfur and selenium radicals for the first time and characterized their structures. X-ray crystallography, electron spin resonance spectroscopy, and density functional theory calculations revealed a three-coordinate hypervalent structure. Utilizing the reversible redox reactions between hypervalent radicals and the corresponding anions bearing Li+, we developed organic radical batteries with these compounds as cathode-active materials. Furthermore, an all-radical battery, with these compounds as the cathode and a silyl radical as the anode, was developed that exhibited a practical discharge potential of similar to 1.8 V and stable cycle performance, demonstrating the potential of these materials for use in metal-free batteries that can replace conventional Li-ion batteries where Li is used in the metal form.

DOI： 10.1021/jacs.5b10774

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A new chromophore, 2-(4-nitrophenyl)benzofuran (NPBF), was designed for two-photon (TP) uncaging using near-IR light. The TP absorption (TPA) cross-sections of the newly designed NPBF chromophore were determined to be 18 GM at 720 nm and 54 GM at 740 nm in DMSO. The TP uncaging reaction of a caged benzoate with the NPBF chromophore quantitatively produced benzoic acid with an efficiency (delta(u)) of similar to 5.0 GM at 740 nm. The TP fragmentation of an EGTA unit was observed with delta(u) = 16 GM. This behavior makes the new chromophore a promising TP photoremovable protecting group for physiological studies.

DOI： 10.1039/c5cc07664a

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5-Hydroxy-10,15,20-triarylporphyrin (oxophlorin) and its Ni(II) and Zn(II) complexes were oxidized with PbO2 to give the corresponding porphyrin meso-oxy radicals as remarkably stable species. These radicals were fully characterized with X-ray diffraction analysis, UV/vis/NIR absorption and ESR spectroscopies, magnetic susceptibility measurement, electrochemical studies, and theoretical calculations. Free-base radical and its Ni(II) complex have been shown to exist as a monoradical in solution, while the Zn(II) complex exists in an equilibrium between monomer (doublet monoradical) and dimer (a non-Kekule singlet biradicaloid) with a dimerization constant of K-D = 3.0 x 10(5) M-1 in noncoordinating CH2Cl2 but becomes a pyridine-coordinated monoradical upon addition of pyridine. Variable temperature magnetic susceptibility measurements of these radicals revealed different magnetic interactions in the solid-states, which has been interpreted in terms of their different packing structures in a microscopic sense. These radicals undergo one-electron oxidation and reduction in a reversible manner within narrow potential windows of 0.57-0.82 V. Finally, one-electron oxidation of Ni(II) and Zn(II) porphyrin meso-oxy radicals with tris(4-bromophenyl)aminium hexachloroantimonate furnished oxophlorin pi-cations, which displayed nonaromatic closed-shell character, NIR absorption, and significant double bond character of the C-O bond.

DOI： 10.1021/jacs.5b11223

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

H-1 NMR (nuclear magnetic resonance) and high-field ESR (electron spin resonance) measurements were carried out for self-doped organic conductors in the ammonium tetrathiapentalene carboxylate (TTPCOO)(2)[(NH41+)(1-x)(NH30)(x)] system. While the pristine TTPCOOH molecule is closed-shell, self-doped carriers are generated by substitution of the carboxyl proton by (NH30) and (NH41+), which can be regarded as a charge reservoir. The pi-extended system TTPCOO has a uniaxial g-tensor, indicating a 2D isotropic structure such as a herring-bone-like or parallel cross donor arrangement. The NMR-relaxation rate indicated the Korringa relation in the temperature dependence, and the ESR linewidth followed the Elliot mechanism. Both of these observations provide supporting evidence for a stable metallic state. In this paper, we introduce self-doped organic conductors as a branch of materials design, and emphasize that advanced magnetic resonance measurements are powerful tools for developing functional materials. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssr.201510206

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCI PUBL CO INC  

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

By developing metallophthalocyanines and diimides as electron-donating and -accepting building blocks, herein, we report the construction of new electron donor-acceptor covalent organic frameworks (COFs) with periodically ordered electron donor and acceptor pi-columnar arrays via direct polycondensation reactions. X-ray diffraction measurements in conjunction with structural simulations resolved that the resulting frameworks consist of metallophthalocyanine and diimide columns, which are ordered in a segregated yet bicontinuous manner to form built-in periodic pi-arrays. In the frameworks, each metallophthalocyanine donor and diimide acceptor units are exactly linked and interfaced, leading to the generation of superheterojunctionsa new type of heterojunction machinery, for photoinduced electron transfer and charge separation. We show that this polycondensation method is widely applicable to various metallophthalocyanines and diimides as demonstrated by the combination of copper, nickel, and zinc phthalocyanine donors with pyrommellitic diimide, naphthalene diimide, and perylene diimide acceptors. By using time-resolved transient absorption spectroscopy and electron spin resonance, we demonstrated that the COFs enable long-lived charge separation, whereas the metal species, the class of acceptors, and the local geometry between donor and acceptor units play roles in determining the photochemical dynamics. The results provide insights into photoelectric COFs and demonstrate their enormous potential for charge separation and photoenergy conversions.

DOI： 10.1021/jacs.5b03553

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Treatment of meso-chlorosubporphyrin with potassium hydroxide in DMSO followed by aqueous work up and recrystallization gave a cyclic trimer consisting of meso-hydroxysubporphyrin units linked between the central boron atoms and meso-hydroxy groups. Solutions of this trimer are nonfluorescent, but become fluorescent when exposed to acid or base, since hydrolytic cleavage of the axial BO bonds generates the meso-hydroxysubporphyrin monomer or its oxyanion. Ring cleavage of the trimer was also effected by reaction with phenylmagnesium bromide to produce meso-hydroxy-B-phenyl subporphyrin, which can be quantitatively oxidized with PbO2 to furnish a subporphyrin meso-oxy radical as a remarkably stable species as a result of spin delocalization over almost the entire molecule.

DOI： 10.1002/anie.201501592

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We have clarified and observed the high electron affinity of pinB-BMes(2) (1; Mes = mesityl, pin = pinacolato). By using electrochemistry, it was shown that 1 has a higher electron affinity than those of B(2)pin(2) and Mes(3)B. One-electron reduction of 1 gave the corresponding radical anion. The ESR spectroscopy and DFT calculation revealed the unsymmetrical distribution of electron density over the B-B bond. UV/Vis spectroscopy showed that the SOMO-related absorption supports the deep purple color of the radical anion. DFT studies on the torsion angle dependency of the LUMO levels and relative energies revealed the reason why 1 has high electron affinity as a result of the substituent effect of the Bpin group.

DOI： 10.1002/chem.201406609

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New allene compounds, 5c and 5d, bearing 1,8-dichloroacridene moieties were synthesized, and the oxidation of 5c and 5d was performed to generate thermally stable triplet carbenes. Since the oxidation resulted in the formation of decomposition products, the photolysis of brominated allene compound 18 was performed. UV-vis measurement at low temperatures indicated the generation of intermediates with decreasing starting material 18, although the efficiency of photolysis was quite low. ESR and electron spin transient nutation (ESTN) spectra suggested that the multiplicity of intermediates is triplet, probably the target triplet carbene 6d is generated. In terms of |D| values of the intermediates, ESR showed that unpaired electrons are more effectively delocalized in 6d by the introduction of nitrogen atoms in the skeleton (biradical character in Scheme1). The observed triplet species 6d was not stable enough to isolate. Copyright (c) 2014 John Wiley & Sons, Ltd.

DOI： 10.1002/poc.3398

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

The first examples of pyrrole-and thiophene-bridged 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 pi-system. In particular, the pyrrole-bridged 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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DOI： 10.1002/anie.201505130

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

Materials based on biradicals/biradicaloids have potential applications for organic electronics, photonics and spintronics. In this work, we demonstrated that hybridization of porphyrin and polycyclic aromatic hydrocarbon could lead to a new type of stable biradicals/biradicaloids with tunable ground state and physical property. Mono- and bis-phenalenyl fused porphyrins 1 and 2 were synthesized via an intramolecular Friedel-Crafts alkylation-followed-by oxidative dehydrogenation strategy. Our detailed experimental and theoretical studies revealed that 1 has a closed-shell structure with a small biradical character (y = 0.06 by DFT calculation) in the ground state, while 2 exists as a persistent triplet biradical at room temperature under inert atmosphere. Compound 1 underwent hydrogen abstraction from solvent during the crystal growing process while compound 2 was easily oxidized in air to give two dioxo-porphyrin isomers 11a/11b, which can be correlated to their unique biradical character and spin distribution. The physical properties of 1 and 2, their dihydro/tetrahydro-precursors 7/10, and the dioxo-compounds 11a/11b were investigated and compared.

DOI： 10.1039/c4sc03866e

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Regulation of electron transfer on organic substances by external stimuli is a fundamental issue in science and technology, which affects organic materials, chemical synthesis, and biological metabolism. Nevertheless, acid/base-responsive organic materials that exhibit reversible electron transfer have not been well studied and developed, owing to the difficulty in inventing a mechanism to associate acid/base stimuli and electron transfer. We discovered a new phenomenon in which N-N linked bicarbazole (BC) and tetramethylbiacridine (TBA) derivatives undergo electron transfer disproportionation by acid stimulus, forming their stable radical cations and reduced species. The reaction occurs through a biradical intermediate generated by the acid-triggered N-N bond cleavage reaction of BC or TBA, which acts as a two electron acceptor to undergo electron transfer reactions with two equivalents of BC or TBA. In addition, in the case of TBA the disproportionation reaction is highly reversible through neutralization with NEt3, which recovers TBA through back electron transfer and N-N bond formation reactions. This highly reversible electron transfer reaction is possible due to the association between the acid stimulus and electron transfer via the acid-regulated N-N bond cleavage/formation reactions which provide an efficient switching mechanism, the ability of the organic molecules to act as multi-electron donors and acceptors, the extraordinary stability of the radical species, the highly selective reactivity, and the balance of the redox potentials. This discovery provides new design concepts for acid/base-regulated organic electron transfer systems, chemical reagents, or organic materials.

DOI： 10.1039/c5sc00946d

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

Ordered one-dimensional open channels represent the typical porous structure of two-dimensional covalent organic frameworks (COFs). Here we report a general synthetic strategy for converting these open lattice structures into ordered donor acceptor heterojunctions. A three-component topological design scheme was explored to prepare electron-donating intermediate COFs, which upon click reaction were transformed to photoelectric COFs with segregated donor acceptor alignments, whereas electron-accepting buckyballs were spatially confined within the nanochannels via covalent anchoring on the channel walls. The donor acceptor heterojunctions trigger photoinduced electron transfer and allow charge separation with radical species delocalized in the pi-arrays, whereas the charge separation efficiency was dependent on the buckyball content. This new donor acceptor strategy explores both skeletons and pores of COFs for charge separation and photoenergy conversion.

DOI： 10.1021/ja502692w

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DOI： 10.1002/anie.201405509

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

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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Polycyclic hydrocarbons (PHs) with a singlet biradical ground state have recently attracted extensive interest in physical organic chemistry and materials science. Replacing the carbon radical center in the open-shell PHs with a more electronegative nitrogen atom is expected to result in the more stable aminyl radical. In this work, two kinetically blocked stable/persistent derivatives (1 and 2) of indolo[2,3-b]carbazole, an isoelectronic structure of the known indeno[2,1-b]fluorene, were synthesized and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate biradical character (y(0) = 0.269) and a small singlet-triplet energy gap (Delta E-S-T congruent to -1.78 kcal mol(-1)), while the more extended dibenzo-indolo[2,3-b]carbazole 2 exhibits a quinoidal closed-shell ground state. The difference can be explained by considering the number of aromatic sextet rings gained from the closed-shell to the open-shell biradical resonance form, that is to say, two for compound 1 and one for compound 2, which determines their different biradical characters. The optical and electronic properties of 2 and the corresponding aromatic precursors were investigated by one-photon absorption, transient absorption and two-photon absorption (TPA) spectroscopies and electrochemistry. Amphoteric redox behaviour, a short excited lifetime and a moderate TPA cross section were observed for 2, which can be correlated to its antiaromaticity and small biradical character. Compound 2 showed high reactivity to protic solvents due to its extremely low-lying LUMO energy level. Unusual oxidative dimerization was also observed for the unblocked dihydro-indolo[2,3-b]carbazole precursors 6 and 11. Our studies shed light on the rational design of persistent aminyl biradicals with tunable properties in the future.

DOI： 10.1039/c4sc01843e

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DOI： 10.1002/anie.201309921

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The synthesis of high-spin polycyclic hydrocarbons is very challenging due to their extremely high reactivity. Herein, we report the synthesis and characterization of a kinetically blocked 1,14:11,12-dibenzopentacene, DP-Mes, which represents a rare persistent triplet diradical of a non-Kekule polycyclic benzenoid hydrocarbon. In contrast to its structural isomer 1,14:7,8-dibenzopentacene (heptazethrene) with a singlet biradical ground state, DP-Mes is a triplet diradical as confirmed by ESR and ESTN measurements and density functional theory calculations. DP-Mes also displays intermolecular antiferromagnetic spin interactions in solution at low temperature.

DOI： 10.1039/c3sc53015a

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Ammonium tetrathiapentalene carboxylate [(TTPCOO)(2)NH4] was prepared via protonic defect-induction doping without electrochemical oxidation. The high electric conductivity of 13 S cm(-1) and Pauli paramagnetic-like behavior of magnetic susceptibility in a wide temperature range exhibit a melting of the charge degrees of freedom induced by a mobile dopant in a salt bridge. Solid-state H-1 NMR strongly indicates a stable metallic state of this compound down to 4 K.

DOI： 10.1039/c4cc00678j

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Three kinds of para-phenylenediamine (PDA) derivatives bearing nitronyl nitroxide (NN) groups were prepared and characterized on the basis of the electrochemical, electron spin resonance (ESR) spectroscopic, absorption spectroscopic, and magnetic susceptibility measurements. It was clarified that the oxidation potential of the central PDA unit is strongly influenced by the numbers of substituted electron-withdrawing NN groups. In addition, the intervalence charge transfer in the central PDA unit was detected in the monocationic states of the PDAs with two NN groups, indicating the coexistence of the localized spins and the delocalized spin on theses molecules. Moreover, pulsed ESR measurements confirmed that the delocalized spin on the central PDA unit and the localized two spins on the NN groups were ferromagnetically coupled in the monocationic states.

DOI： 10.1021/jp4095613

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Octaazacyclophanes, octaaza[18]m,p,m,p,m,p,m,p-cyclophane (2) and octaaza[18]m,p,p,p,m,p,p,p-cyclophane (3), as ring-size extended congeners of tetraaza[14]m,p,m,p-cyclophane were synthesized, and the electronic states of their polycationic species were investigated by quantum chemical calculations, electrochemical measurements (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)), UV-vis-NIR spectroelectrochemical measurements, and pulsed electron spin resonance (ESR) spectroscopy. These octaazacyclophanes exhibited multiredox activities depending on different linkage patterns along the macrocyclic molecular skeletons, and both molecules were oxidizable up to their respective octacations. Spectroelectrochemical measurements demonstrated that p-phenylenediamine (PD) moieties in 2 could be converted from the semiquinoidal structure to the quinoidal sturcture with increasing oxidation number, whereas higher oxidation states of 3 did not show definite quinoidal deformation of PD moieties. A pulsed ESR spectrum gave evidence about formation of the almost pure spin-triplet state for 3 2+, whereas the high-spin states of 22+ and 24+ are virtually degenerate with the competing low-spin states even at low temperatures, probably due to the fragility of spin-coupling pathway caused by facile conformational changes. © 2013 American Chemical Society.

DOI： 10.1021/jo3026884

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Single crystal X-ray analysis has been used as a powerful method to determine the structure of molecules. However, crystallographic data containing helium has not been reported, owing to the difficulty in embedding helium into crystalline materials. Here we report the X-ray diffraction study of He@C-60 and the clear observation of a single helium atom inside C-60. In addition, the close packing of a helium atom and a nitrogen atom inside fullerenes is realized using two stepwise insertion techniques, that is, molecular surgery to synthesize the fullerenes encapsulating a helium atom, followed by nitrogen radio-frequency plasma methods to generate the fullerenes encapsulating both helium and nitrogen atoms. Electron spin resonance analysis reveals that the encapsulated helium atom has a small but detectable influence on the electronic properties of the highly reactive nitrogen atom coexisting inside the fullerene, suggesting the potential usage of helium for controlling electronic properties of reactive species.

DOI： 10.1038/ncomms2574

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DOI： 10.1002/anie.201209513

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Alkyloctamethylferrocenium salts with the Tf2N anion ([Fe(C5Me4CnH2n+1)(C5Me4H)][Tf2N]; Tf2N = bis(trifluoromethanesulfonyl)amide) were prepared, and their ionic liquid properties, thermal properties, crystal structures, and magnetic properties were investigated. The melting points of the Tf2N salts were near room temperature, and decreased with increasing alkyl chain length up to n = 8 and then increased. The salts with PF6 and NO3 anions were also prepared. The melting points of the PF6 salts were higher than 100 degrees C. Most of these salts exhibited phase transitions in the solid state. The sum of the entropies of the melting and solid phase transitions was nearly independent of the alkyl chain length for salts with short alkyl chains, whereas those for salts with longer alkyl chains (n >= 10 for Tf2N salts, n >= 6 for PF6 salts) increased with increasing alkyl chain length. Crystal structure determinations revealed that the short chain salts form simple alternately packed structures of cations and anions in the solid state, and that the long chain salts form lamellar structures, in which the alkyl chains are aligned parallel between the layers. The effects of magnetic fields on the crystallization of the paramagnetic ionic liquids were investigated, and revealed that the Tf2N salts with n = 4 exhibited magnetic orientation when solidified under magnetic fields. The magnetic orientation was shown to be a bulk phenomenon, and the importance of the magnetic anisotropy of the crystal structure was suggested in comparison with the response of other Tf2N salts.

DOI： 10.1039/c3dt00084b

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We report the synthesis and structural characterization of large pore covalent organic frameworks (COFs) integrated with donor and acceptor building blocks. The donor and acceptor, based on triphenylene and diimide, respectively, are topologically linked to form COFs with stacked donor and acceptor columns and 5.3 nm width channels, which show high crystallinity and large surface area. By varying donor-acceptor structure in conjunction with time-resolved spectroscopy, these large-pore COFs constitute benchmark frameworks to elucidate not only the importance of donor-acceptor pairing but also the role of lattice structure in charge transfer and separation, thereby casting a general principle for the structural design of optoelectronic and photovoltaic COFs.

DOI： 10.1039/c3sc52034j

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

An organic insulating crystal reversibly becomes a magnetic conductor under UV irradiation. The rapid and qualitative change in the physical properties is wavelength selective and explained by charge transfer between donor and photochemically active acceptor molecules. The photochemical redox reaction in the crystal produces a partially filled band and localized spins simultaneously.

DOI： 10.1002/adma.201203153

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DOI： 10.1002/ange.201107104

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

DOI： 10.1002/anie.201206831

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The dry grinding of a mixture of bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF) and silica nanoparticles has produced powdery (BEDT-TTF)-silica nanocomposites. The (BEDT-TTF)-silica nanocomposites are readily doped with iodine in hexane dispersion to give powdery nanocomposites of (BEDT-TTF)(2)I-3-silica. XRD and TEM measurements suggest that (BEDT-TTF)(2)I-3 in the nanocomposite exists as shell layers of core-shell-type nanoparticles and as nanometre-sized crystals incorporated into hollow sites of aggregated silica nanoparticles. Magnetic susceptibility measurements reveal that the nanocomposites accompanied a large number of Curie spins attributable to surface molecules of the core-shell-type nanoparticles. The nanocomposites show a magnetic susceptibility change corresponding to the metal-insulator transition of alpha-(BEDT-TTF)(2)I-3 in a broad temperature range of 110-140 K, which is attributed to the properties of the nanocrystalline components. Doping in diethyl ether dispersion leads to higher amounts of the nanocrystalline component being obtained. The doping of (BEDT-TTF)-silica nanocomposites by dry grinding produces a paramagnetic powder containing amorphous (BEDT-TTF)(2)I-3, which possesses a Curie spin concentration of 50%. The effects of annealing on these nanocomposites are investigated. The electrical conductivity of the compaction pellets of (BEDT-TTF)-silica nanocomposites is enhanced by iodine doping to reach approximately 10(-6) S cm(-1), but the value is much lower than that of the bulk crystals (10(1) S cm(-1))

DOI： 10.1039/c1ra00590a

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DOI： 10.1002/anie.201203451

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Magnetic properties in the quasi-one-dimensional organic salt, (TMTTF) 2SbF6, where TMTTF is tetramethyltetrathiafulvalene, are investigated by 13C NMR under pressures. Antiferromagnetic phase transition at ambient pressure (AFI) is confirmed. Charge ordering is suppressed by pressure and is not observed under 8 kbar. For 5&lt
P&lt
20 kbar, a sharp spectrum and the rapid decrease of the spin-lattice relaxation rate 1/T1 were observed below about 4K, which is attributed to a spin-gap transition. Above 20 kbar, an extremely broadened spectrum and a critical increase of 1/T1 were observed. This indicates that the system enters into another antiferromagnetic phase (AFII) under pressure. The slope of the antiferromagnetic phase transition temperature TAFII, dT AFII/dP, is positive, while TAFI decreases with pressure. The magnetic moment is weakly incommensurate with the lattice at 30 kbar. © 2011 American Physical Society.

DOI： 10.1103/PhysRevB.84.115140

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

Magnetic properties in the quasi-one-dimensional organic salt, (TMTTF)(2)SbF6, where TMTTF is tetramethyltetrathiafulvalene, are investigated by C-13 NMR under pressures. Antiferromagnetic phase transition at ambient pressure (AFI) is confirmed. Charge ordering is suppressed by pressure and is not observed under 8 kbar. For 5 < P < 20 kbar, a sharp spectrum and the rapid decrease of the spin-lattice relaxation rate 1/T-1 were observed below about 4 K, which is attributed to a spin-gap transition. Above 20 kbar, an extremely broadened spectrum and a critical increase of 1/T-1 were observed. This indicates that the system enters into another antiferromagnetic phase (AFII) under pressure. The slope of the antiferromagnetic phase transition temperature T-AFII, dT(AFII)/dP, is positive, while TAFI decreases with pressure. The magnetic moment is weakly incommensurate with the lattice at 30 kbar.

DOI： 10.1103/PhysRevB.84.115140

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The dimetallic endohedral heterofullerene (EHF), Gd-2@C79N, was prepared and isolated in a relatively high yield when compared with the earlier reported heterofullerene, Y-2@C79N. Computational (DFT), chemical reactivity, Raman, and electrochemical studies all suggest that the purified Gd-2@C79N, with the heterofullerene cage, (C79N)(5-) has comparable stability with other better known iso electronic metallofullerene (C-80)(6-) cage species (e.g., Gd3N@C-80). These results describe an exceptionally stable paramagnetic molecule with low chemical reactivity with the unpaired electron spin density localized on the internal diatomic gadolinium cluster and not on the heterofullerene cage. EPR studies confirm that the spin state of Gd-2@C79N is characterized by a half-integer spin quantum number of S = 15/2. The spin (S =1/2) on the N atom of the fullerene cage and two octet spins (S = 7/2) of two encapsulated gadoliniums are coupled with each other in a ferromagnetic manner with a small zero-field splitting parameter D. Because the central line of Gd-2@C79N is due to the Kramer's doublet with a half-integer spin quantum number of S = 15/2, this relatively sharp line is prominent and the anisotropic nature of the line is weak. Interestingly, in contrast with most Gd3+ ion environments, the central EPR line (g = 1.978) is observable even at room temperature in a toluene solution. Finally, we report the first EHF derivative, a diethyl bromomalonate monoadduct of Gd-2@C79N, which was prepared and isolated via a modified Bingel-Hirsch reaction.

DOI： 10.1021/ja202011u

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The cyclic host cyclo-[Pc-u](2) carrying two covalently connected Cu(II) porphyrin units can accommodate La@C-82, a paramagnetic endohedral metallofullerene, in its cavity to form the inclusion complex cyclo-[Pc-u](2)superset of La@C-82, which can be transformed into the caged complex cage-[Pc-u](2)superset of La@C-82 by ring-closing olefin metathesis of its side-chain olefinic terrnini. On the basis of electron spin resonance (ESR) and electron spin transient nutation (ESTN) studies, cyclo-[Pc-u](2)superset of La@C-82 is the first ferromagnetically coupled inclusion complex featuring La@C-82, whereas cage-[Pc-u](2)superset of La@C-82 is ferrimagnetic.

DOI： 10.1021/ja203491s

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To elucidate the electronic state that exists in the boundary region between the spin-singlet phase and the high-pressure side antiferromagnetic phase in the modified generalized phase diagram, we carried out x-ray diffraction, electron spin resonance, and nuclear magnetic resonance measurements of the tetramethyl-tetrathia-fulvalene (TMTTF) family salt, (TMTTF)2I. The unit-cell volume of (TMTTF)2I is between that of (TMTTF)2Br and (TMTTF)2PF6. We found that (TMTTF)2I undergoes a spin-singlet phase transition at 21 K without involving paramagnetic charge-ordering phase. Therefore, the charge-ordering transition is not necessary for the spin-singlet transition of TMTTF salts as seen in other conventional spin-singlet salts. Finally, we discuss possible mechanisms of the spin-singlet phase transition. © 2011 American Physical Society.

DOI： 10.1103/PhysRevB.83.184419

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To elucidate the electronic state that exists in the boundary region between the spin-singlet phase and the high-pressure side antiferromagnetic phase in the modified generalized phase diagram, we carried out x-ray diffraction, electron spin resonance, and nuclear magnetic resonance measurements of the tetramethyl-tetrathiafulvalene (TMTTF) family salt, (TMTTF)(2)I. The unit-cell volume of (TMTTF)(2)I is between that of (TMTTF)(2)Br and (TMTTF)(2)PF6. We found that (TMTTF)(2)I undergoes a spin-singlet phase transition at 21 K without involving paramagnetic charge-ordering phase. Therefore, the charge-ordering transition is not necessary for the spin-singlet transition of TMTTF salts as seen in other conventional spin-singlet salts. Finally, we discuss possible mechanisms of the spin-singlet phase transition.

DOI： 10.1103/PhysRevB.83.184419

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The spin dynamics of photoconductive tetrathiafulvalene (TTF) derivatives containing 2,5-diphenyl-1,3,4-oxadiazole (PPD) was examined using time-resolved electron spin resonance (TR-ESR) spectroscopy. TR-ESR signals of a frozen solution sample under visible excitation were attributed to the excited triplet state T-1, which was populated via intersystem crossing from the excited singlet state S-1 as confirmed by TR-ESR spectral simulations. From DFT calculations, the spin-density distribution of the T-1 state was found to be concentrated around the linker between the TTF and PPD molecules.

DOI： 10.1246/cl.2011.292

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A paramagnetic ferrocenium-based ionic liquid that exhibits a magnetic memory effect coupled with a liquid-solid phase transformation has been developed. Based on field alignment of the magnetically anisotropic ferrocenium cation, the magnetic susceptibility in the solid state can be tuned by the weak magnetic fields (<1 T) of permanent magnets.

DOI： 10.1039/c0cc05820c

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Magnetic investigations, including static magnetic susceptibility and high-field electron spin resonance (ESR) measurements, were carried out for an organic conductor, (TTFCOO)[(NH4+1)(1-x)(NH3)(x)]. Anisotropic ESR parameters were determined for powder samples using a high-frequency W-band (93.9817 GHz) ESR spectrometer. The observed principal values of the g-tensor and quantum chemical calculation results indicate that the observed spin is distributed on quasi-hole-like TTF skeletons, and that the TTFCOO mainframe partially becomes a neutral radical. The temperature dependence of the spin susceptibility is well fitted with a Curie-Weiss term and an activation-type term, with the activation-type term dominant at high temperatures. The high absolute value of the spin susceptibility and the extremely small activation energy, Delta, indicate that a quasi-degenerate (metallic) state is stabilized in (TTFCOO)[(NH4+1)(1-x)(NH3)(x)], although the weakly temperature-dependent ESR linewidth indicates a localized characteristic. A novel type of carrier generation, self-doping, was discussed.

DOI： 10.1143/JPSJ.79.053701

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The spin dynamics in the vicinity of the spin-gap phase transition for the organic conductor (TMTTF)(2)PF6 were examined by pulsed-ESR spectroscopy. An anomaly in the relaxation time was observed in this intermediate region between the ground state and the high-temperature phase and was associated with the charge re-orientation originating in the transverse magnetic interaction. The calculation of the overlap integrals implied considerable inter-chain interactions. The transverse magnetic interaction plays an important role of the spin-gap phase transition in (TMTTF)(2)PF6.

DOI： 10.1143/JPSJ.79.043702

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Spin dynamics of S=2 triangluar lattice antiferromagnet have been investigated by the submillimeter and the millimeter wave ESR measurements of polycrystalline samples of InMnO3. Single absorption line is observed in whole temperature range from 2.0 K to 265 K. The resonance field shifts due to the development of internal field are observed below 40 K. The spin dynamics of InMnO3 will be discussed in connection with other triangluar lattice antiferromagnets.

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In this paper, we introduce the electronic states and electronic properties of molecular solid especially charge transfer salts and radical salts in the aspect of photo-induced phase transition and related phenomena. The characteristic features of molecular solid, which deeply related to photo-induced phase transition, are as following:(1) low-dimensional electronic states originated from anisotropic interaction,(2) strong electronic correlation induced by low carrier concentration,(3) lattice softness which causes competition of electronic phases with pressure and thermal contraction,(4) internal-freedom, namely, molecular motions. We propose strategies for exploring possible candidates for forthcoming materials with photo-induced phase transition.

DOI： 10.2184/lsj.36.339

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ESR and H-1 NMR investigations were performed on iodine-doped HBC nanotubes to understand the low-temperature electronic states and carrier dynamics. Using ESR measurements, we clarified that the charged carriers induced by iodine-doping possess spins, and we found two kinds of spin species with different doping levels. The ESR results indicate the itinerant features down to 170 K. The H-1 T-1(-1) for the heavy-iodine-doped HBC nanotubes follows T-0.5 and exhibits a characteristic frequency dependence. We propose that the spin excitation propagates along the one-dimensional helical chain.

DOI： 10.1143/JPSJ.77.034710

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C-13 nuclear magnetic resonance (NMR) investigations were carried out for a one-dimensional organic conductor, (TMTTF)(2)PF6, to determine the charge dynamics and configuration in the proximity of the spin-Peierls phase-transition temperature, T-sP. Although no obvious NMR line splitting associated with the charge-ordering transitions in the intermediate paramagnetic states was observed, the charge separation amplitude was estimated to be rho co similar to 0.14 using the C-13 NMR spin-lattice relaxation rates for the distinct lines. The abrupt decrease in the NMR linewidth below 25 K and the small anisotropy of the NMR linewidth in the spin-Peierls phase indicate the possible redistribution of the charge separation in the proximity of T-sP. The low-temperature electronic states of (TMTTF)(2)PF6 are discussed from a microscopic point of view.

DOI： 10.1143/JPSJ.76.064715

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The electronic states of M-DNA doped with M = Mg, Ca, Zn, Mn, Fe are investigated mainly with magnetic properties. In the "wet" condition the Mn ions of Mn-DNA form a 1-D chain in the center of a DNA double helix, as evidenced from the formation of the unnatural base pair combination with M, poly(dA)-M-poly(dC), but in the "dry" condition they form a 3-D network with the antiferromagnetic ground state around 0.4 K with the superexchange coupling via water molecules. The valence of 3+ is found only in Fe-DNA, from which the base pi-band obtains pi charge carriers.

DOI： 10.1143/JPSJ.76.043801

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C-13 NMR measurements were performed for a one-dimensional organic conductor, (TMTTF)(2)ReO4. The existence of an intermediate charge ordering (CO) phase was clarified for a TMTTF salt with a T-d symmetry counter anion by the C-13 NMR absorption line and spin-lattice relaxation rate, C-13 T-1(-1). The C-13 NMR spectra, which are characteristic of nuclei in equivalent molecules at room temperature, indicated two inequivalent molecules with unequal electron densities below 225 K. Moreover, the spin-singlet transition associated with ReO4 anion ordering was confirmed at around 158 K by C-13 NMR. The C-13 NMR lines show a marked change at 158 K. The possible redistribution of the electronic charge at the anion ordering temperature as well as the origin of the charge ordering phenomena are discussed.

DOI： 10.1143/JPSJ.75.013707

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DOI： 10.1109/INTMAG.2006.374965

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ESR, NMR and X-ray measurements were performed for pristine and fully perdeuterio-TMTTF, TMTTF-d(12) salts. Significant enhancement by deuteration of the charge-order phase transition temperature, Tco, was observed in ESR measurements for all (TMTTF)(2)X salts measured. No obvious relation between the SbF6 anion motion and the TMTTF charge-order was found by F-19 NMR. We also performed single crystal X-ray measurements to understand the deuteration effects and temperature dependence of the crystal structure. A possible relationship between the Tco's and crystallographical parameters is proposed. The deuteration effects and possible origin of the charge-ordering transition of TMTTF salts are discussed.

DOI： 10.1143/JPSJ.74.3288

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From dielectric permittivity measurements, we show that deuteration yields a large increase of the transition temperature for the charge ordered state of (TMTTF)(2)X (X = AsF6, SbF6, ReO4) salts. We propose an explanation of this phenomenon, suggesting that deuteration induces a modification of the (TMTTF)(2)X crystal unit cell.

DOI： 10.1088/0953-8984/17/41/L01

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Poly(ethylenedioxy-substituted terthiophene -fullerene) was electrochemically synthesized on an ITO electrode, and its electronic and optical properties were measured. A large photocurrent of more than 3 mu A/cm(2) was observed by irradiation at 50 mW/cm(2) with a halogen lamp using a wet cell containing 5 mM methyl viologen.

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This work discusses an issue caused by omitting the fourth-order zero-field splitting (ZFS) terms in the analysis of random-orientation EPR spectra. Eu(II)-doped strontium aluminates were employed as a model system of the S-state lanthanoid ions, which have relatively large second-rank ZFS components, comparable to the conventional X-band microwave energy. The initial estimation of second- and fourth-rank ZFS components was acquired uniquely from the W-band spectrum based on a perturbation treatment of the spin Hamiltonian, and they were refined by a hybrid-eigenfield simulation approach. A parallel simulation of the X- and W-band spectra with the refined parameters reasonably reproduced both the observed spectra. The reliability of the parameters was also verified by reproducing the off-principal-axis extra lines arising from the M-S = 1/2 <----> 1/2 transition observed in the W-band spectrum. By comparison with an analysis based on the spin Hamiltonian omitting the fourth-order terms, it was concluded that omitting these terms results in an erroneous determination of the rhombic parameter (E) of the second-rank ZFS tensor. The obtained reliable second-rank ZFS tensors enabled us to invoke the superposition model, determining their principal-axis orientation. This is the first report of such relative orientation determined for Eu(II)-doped strontium aluminates.

DOI： 10.1021/jp030819

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

High-spin Co(II) complexes (S = 3/2) with hydrogen bonding network were synthesized as models for magnetic quantum wires or 2D magnetic network systems. Their magnetic properties were characterized in terms of the SQIUD measurement. An analysis for the magnetic susceptibilities assuming an effective angular momentum L'=1 reproduced the experimental temperature dependences of the susceptibilities. In order to evaluate intermolecular magnetic interactions, it turned out that models beyond Heisenberg-Dirac exchange Hamiltonian are required for the analysis.

DOI： 10.1016/S0379-6779(02)01047-0

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A variety of directly-linked diporphyrins can be prepared by an oxidative coupling reaction of 5,15-diaryl metalloporphyrins. Regioselectivity of the coupling reaction depends on the metal in the porphyrin core; Zn-II-porphyrins favor meso-meso coupling and Pd-II-porphyrins favor meso-beta coupling. beta-beta Linked diporphyrins were isolated for the first time from the oxidation of 5,15-diaryl Pd-II-porphyrin with DDQ and Sc(OTf)(3). Copyright (C) 2003 Society of Porphyrins & Phthalocyanines.

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Cu (II) complexes with violuric acid ligand were synthesized, and the relationship between the structures and magnetic properties of these complexes were examined, focussing on the role of the hydrogen-bonded network on their magnetic properties. The X-ray crystal structural analyses show that these complexes form three-dimensional hydrogen-bonded network (1), as well as two-dimensional sheet structures for some cases (2, 3). The temperature dependence of the magnetic susceptibility of 1 revealed the low-dimensional antiferromagnetic interactions. The marked g-shift for L was observed from the temperature dependence of the ESR spectra. From the Xray diffraction at 173 K, it is revealed that the marked g-shift for I originates in the cooperative Jahn-Teller assisted hydrogen-bonding variation.

DOI： 10.1016/S0379-6779(00)00742-6

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DOI： 10.1080/10587259908028860

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.68.2.4.0_749_1

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DOI： 10.11316/jpsgaiyo.68.1.4.0_937_1

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DOI： 10.11316/jpsgaiyo.66.2.4.0_884_1

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DOI： 10.11316/jpsgaiyo.66.2.4.0_884_2

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DOI： 10.11316/jpsgaiyo.66.1.4.0_869_3

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

In this study, we have prepared spirobi(triarylamine)s containing nitroxide groups as localized spin units. In the oxidized states for the spiro molecules, we expected intramolecular ferromagnetic interaction between the localized spins and the delocalized spins. There exists the possibility that the radical cation and di(radical cation) of the spiro molecules are in spin quartet and quintet states, respectively, as a consequence of the intramolecular ferromagnetic interaction. We will report in detail on the electronic structures of the oxidized species on the basis of spectroscopic measurements.

DOI： 10.11494/kisoyuki.2011.0.164.0

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The cyclic host cyclo-[PCu]2 carrying two covalently connected Cu(II) porphyrin units can accommodate La@C82, a paramagnetic endohedral metallofullerene, in its cavity to form the inclusion complex, which can be transformed into the caged complex by ring-closing olefin metathesis of its side-chain olefinic termini. On the basis of electron spin resonance (ESR) and electron spin transient nutation (ESTN) studies, the former complex is the first ferromagnetically coupled inclusion complex featuring La@C82, whereas the latter is ferrimagnetic.

DOI： 10.11494/kisoyuki.2011.0.66.0

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Molecular nano-devices are regarded as one of the next-generation electronic devices, and therefore, many kinds of molecular parts have been prepared to realize desired functionalities. Especially, it is interesting to control the electronic spin in molecular parts, because it will lead to spintronic devices. Here, we report the preparation of a novel hexaazaparacyclophane, in which three para-phenylenediamine units and three anthracene moieties are alternately connected, and moreover, the electronic structure has been clarified on the basis of several spectroscopic measurements. As a result, it has been suggested that intramolecular ferromagnetic interactions occur in the tricationic species of this molecule.

DOI： 10.11494/kisoyuki.2011.0.349.0

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We reported a stable meso-unsubstituted hexaphyrin, meso-free hexaphyrin, and its metal complexes. meso-Diketo hexaphyrin which is remarkably stable and can be manipulated like usual organic molecules was synthesized by the demetalation of the Ni complex. Its structure was determined by X-ray diffraction analysis to be meso,meso-diketo, non-Kekulé biradicaloid hexaphyrin. Singlet ground-state with non-Kekulé structure was revealed by ESR and SQUID measurements. The optical and electrochemical properties will be also reported.

DOI： 10.11494/kisoyuki.2011.0.372.0

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We prepared novel multi-layered aromatic amines. These molecules are the first examples of layered cyclophanes that consist only of aromatic amines. The electronic properties of these molecules were investigated by using cyclic voltammetry, UV-Vis-NIR absorption, and ESR method.

DOI： 10.11494/kisoyuki.2011.0.457.0

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DOI： 10.11316/jpsgaiyo.65.2.4.0_792_3

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DOI： 10.11316/jpsgaiyo.65.2.4.0_792_2

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We report the X-ray irradiation dose dependence of the magnetic susceptibility in kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl (kappa-Cl) and beta'-(BEDT-TTF)(2)ICl2 (beta'-ICl2)The Neel temperature of 27 5 K in kappa-Cl reduces to 24 0 K after irradiation of 240 MGy while that of 22 0 K in beta'-ICl2 does not vary Taking account of the suppressed amplitude of the dicyanamide vibration modes in the infrared spectra of the irradiated kappa-Cl we suggest that X-ray irradiation modifies the anion structure related to the CN group which does not hold in beta -ICl2 (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.10.043

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A meso,meso-diketohexaphyrin was isolated and characterized as a chemically stable non-Kekule singlet biradicaloid. Two unpaired electrons are seemingly delocalized on two tripyrrolic units separated by C=O bonds. These results underscore the potential of expanded porphyrins to achieve unique electronic states.

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C-13 NMR measurements were carried out to understand the chemical pressure effect on the ground state in quasi-one-dimensional (1D) organic complexes using the alloy system (TMTTF)(2)[(AsF6)(x)(SbF6)(1-x)] (x similar to 0.3, 0.5, 0.67). The temperature of the charge-ordering transition decreases with the concentration of AsF6. Additional line splitting and the rapid increase in the spin-lattice relaxation rate, 1/T-1, on cooling for the salt of x similar to 0.3 indicates that the ground state of the salt is antiferromagnetic. In the x similar to 0.67 alloy, the spin gap opens without antiferromagnetic spin correlations. The intermediate salt of x similar to 0.5 is located in the vicinity of the quantum critical region between two phases at low temperatures. The quasi-1D correlation and antiferromagnetic critical behavior are discussed in terms of the power-law behavior of 1/T-1.

DOI： 10.1103/PhysRevB.81.245126

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Magnetic investigations, including static magnetic susceptibility and high-field electron spin resonance (ESR) measurements, were carried out for an organic conductor, (TTFCOO)[(NH4+1)(1-x)(NH3)(x)]. Anisotropic ESR parameters were determined for powder samples using a high-frequency W-band (93.9817 GHz) ESR spectrometer. The observed principal values of the g-tensor and quantum chemical calculation results indicate that the observed spin is distributed on quasi-hole-like TTF skeletons, and that the TTFCOO mainframe partially becomes a neutral radical. The temperature dependence of the spin susceptibility is well fitted with a Curie-Weiss term and an activation-type term, with the activation-type term dominant at high temperatures. The high absolute value of the spin susceptibility and the extremely small activation energy, Delta, indicate that a quasi-degenerate (metallic) state is stabilized in (TTFCOO)[(NH4+1)(1-x)(NH3)(x)], although the weakly temperature-dependent ESR linewidth indicates a localized characteristic. A novel type of carrier generation, self-doping, was discussed.

DOI： 10.1143/JPSJ.79.053701

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The spin dynamics in the vicinity of the spin-gap phase transition for the organic conductor (TMTTF)(2)PF6 were examined by pulsed-ESR spectroscopy. An anomaly in the relaxation time was observed in this intermediate region between the ground state and the high-temperature phase and was associated with the charge re-orientation originating in the transverse magnetic interaction. The calculation of the overlap integrals implied considerable inter-chain interactions. The transverse magnetic interaction plays an important role of the spin-gap phase transition in (TMTTF)(2)PF6.

DOI： 10.1143/JPSJ.79.043702

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DOI： 10.11316/jpsgaiyo.65.1.4.0_862_2

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DOI： 10.11316/jpsgaiyo.65.1.4.0_862_1

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Fully pi-conjugated oligopyrromethene helices coiling two Cu(II) ions were obtained from oxidative cleavage of expanded porphyrins. The Smoothly conjugated backbone structures, distinct near-IR absorption bands, and extended spin-density distributions demonstrated the effective pi-electron delocalization over the whole helices. Magnetic susceptibility and electron spin resonance measurements revealed the antiferromagnetic interaction between the internal Cu(II) ions.

DOI： 10.1021/ja909929s

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C-13 nuclear magnetic resonance (NMR) measurements under the application of hydrostatic pressure were carried out on the one-dimensional organic conductor, (TMTTF)(2)SbF6, to investigate the competed antiferromagnetic and spin-singlet ground states. The charge-ordering (CO) transition temperature, T-CO, (155 K at ambient pressure), decreased to 100 K under a pressure of 5 kbar, and was suppressed above 8 kbar. Under pressures between 5 kbar and 14 kbar, the low-pressure side antiferromagnetic state (AF-I) was suppressed. At the same time, a spin-gap phase was stabilized. Above 17 kbar, another antiferromagnetic phase appeared below approximately 15 similar to 20 K. A possible reentrant antiferromagnetic phase diagram is discussed from a microscopic point-of-view.

DOI： 10.1088/1742-6596/215/1/012063

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DOI： 10.1002/asia.200900619

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para-Phenylene-bridged spirobi(triarylamine) dimer 2, in which a conjugation through four redox-active triarylamine subunits is partially segregated by the unique perpendicular conformation, was prepared and characterized by structural, electrochemical, and spectroscopic methods. Quantum chemical calculations (DFT and CASSCF) predicted that the frontier molecular orbitals of 2 are virtually fourfold degenerate, so that the oxidized states of 2 can give intriguing electronic and magnetic properties. In fact, the continuous-wave ESR spectroscopy of radical cation 2(center dot+) showed that the unpaired electron was trapped in the inner two redox-active dianisyl-amine subunits, and moreover was fully delocalized over them. Magnetic susceptibility measurements and pulsed ESR spectroscopy of the isolated salts of 2, which can be prepared by treatment with SbCl(5), revealed that the generated tetracation 2(4+) decomposed mainly into a mixture of 1) a decomposed tetra(radical cation) consisting of a tri(radical cation) moiety and a trianisylamine radical cation moiety (approximate to 75%) and 2) a diamagnetic quinoid dication in a tetraanisyl-p-phenylendiamine moiety and two trianisylamine radical cation moieties (25%). Furthermore, the spin-quartet state of the tri(radical cation) moiety in the decomposed tetra(radical cation) was found to be in the ground state lying 30 cal mol(-1) below the competing spin-doublet state.

DOI： 10.1002/chem.201000848

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InMnO(3) can be considered a model substance of the S=2 triangular lattice antiferromagnet from the crystal structure. As the magnetic susceptibility with a maximum around 15 K does not show a long-range order in spite of the large negative Weiss temperature of -430 K, spin frustration is expected to occur. We have performed the high-frequency high-field ESR of a powder sample InMnO(3) in the frequency range of 70 to 360 GHz using the pulsed magnetic field up to 16 T together with the conventional X and Q-bamd ESR. The temperature dependence shows the g-shift and the broadening of the linewidth at low temperature, suggesting the development of spin correlation. Moreover, the frequency dependence measurement at 2.0 K suggests the existence of a spin gap. The spin gap is estimated to be about 26.5 GHz (1.2 K). The origin of the spin gap will be discussed in connection with the spin frustration in the system.

DOI： 10.1088/1742-6596/200/2/022041

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DOI： 10.1002/anie.200906017

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The magnetic properties of organic conductor (TMTTF)(2)X (X = Br, PF6, and SbF6), where TMTTF is tetramethyltetrathiafulvalene, were examined by electron spin resonance (ESR) spectroscopy, X-ray diffraction (XRD) of the single crystals, and quantum-chemical calculation of the g-tensor. In the case of salts with bulky counter anions such as the PF6 and SbF6, an anomalous temperature dependence of the g-tensor was observed in the temperature range from 20 to 296 K. This anomalous behavior of the g-tensor signifies the rotation of the principal axes as well as the shift of the principal values. The g-tensor of the Br salt is, however, temperature independent. No remarkable change in the intra-molecular structure as a function of temperature was observed for all salts. On the other hand, the distance between TMTTF and counter-anion molecules obviously decreases as the temperature decreases for the PF6 and SbF6 salts, while thermal contraction is not remarkable for the Br salt. In order to clarify the origin of the anomalous behavior of the g-tensor, we investigated the possibility of deformation of the wave-function by the counter-anion potentials using a quantum-chemical calculation for the actual crystal structures measured at low-temperatures. In this paper, we describe the first direct observation of the deformation of the frontier orbital by the counter anion potential for organic conductors. The intra-molecular spin-distribution as a function of temperature is also discussed from the microscopic point of view.

DOI： 10.1143/JPSJ.78.104713

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A new TMTTF (tetramethyl-tetrathia-fulvalene)-family salt, (TMTTF)(2)TaF6, which has the largest octahedral (O-h) symmetry counter anion among the various salts in the TMTTF family, was prepared. X-ray, static magnetic susceptibility, electron spin resonance (ESR) and nuclear magnetic resonance (NMR) measurements were carried out in order to investigate the electronic state of (TMTTF)(2)TaF6. The unit-cell volume of (TMTTF)(2)TaF6 is larger than that of (TMTTF)(2)MF6 (M = P, As, and Sb). (TMTTF)(2)TaF6 shows the highest charge-ordering phase transition temperature (7(CO) similar to 175 K) among TMTTF salts with the O-h-symmetry Counter anion. These facts indicate that (TMTTF)(2)TaF6 is located on the most negative side in the generalized phase-diagram for TMTCF family salts. (TMTTF)(2)TaF6 undergoes an anti ferromagnetic transition around 9 K. It turned out the phase diagram needs to be modified.

DOI： 10.1143/JPSJ.78.104717

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Metalation of meso-free 5,10,20,25-tetrakis(pentafluorophenyl)substituted [26]hexaphyrin(1.1.1.1.1.1) (4) with Cu-II and Zn-II ions afforded homodinuclear complexes 6 and 7, respectively. A demetalation-remetalation protocol provided monozinc(II) complex 9 selectively, from which copper(II)-zinc(II) heterodinuclear complex 10 was prepared effectively.

DOI： 10.1021/ic900084p

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High-spin alignment for dicationic, tricationic, tetracationic and hexacationic species of a meta-para-linked oligoarylamine was accomplished by incorporating cyclophane skeletons into the oligomer backbone.

DOI： 10.1039/b907792h

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C-13 nuclear magnetic resonance (NMR) investigations were performed on the one-dimensional organic conductor (TMTTF)(2)SbF6 to clarify its electronic properties in the proximity of the ground states. An abrupt broadening of C-13 NMR absorption lines below 8 K (T-N=8 K), confirmed a long-range antiferromagnetic phase transition. Below T-N, the absorption lines are composed of four distinct broad lines, indicating a commensurate magnetic structure. The amplitude of staggered magnetization, rho, is comparable to (TMTTF)(2)Br, and on the order of 0.1 mu(B) according to the splitting of C-13 NMR lines at 3 K.

DOI： 10.1088/1742-6596/150/4/042137

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DOI： 10.1002/anie.200902901

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Free base porphyrin sheet 5 was prepared by demetalation of zinc complex 1, which was now more conveniently prepared in 30% yield by oxidation of a mixture of tetraporphyrins, 8, 9, and 11. The 1H NMR spectrum of 5 shows no indication of an aromatic ring current for the porphyrin rings and evidences the freezing of the pyrrolic NH protons at the most inner and outer corner positions, both of which contrast sharply with strong aromatic ring currents and rapid NH tautomerism of normal porphyrins. DFT calculations supported the experimental results, suggesting that the enforced planar COT core causes these unique properties. The free base 5 was transformed into Cu(II) complex 6 that exhibits antiferromagnetic interaction among the Cu(II) ions with J=-1.16 cm-1. © 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2008.08.072

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ESR and H-1 NMR investigations were performed on iodine-doped HBC nanotubes to understand the low-temperature electronic states and carrier dynamics. Using ESR measurements, we clarified that the charged carriers induced by iodine-doping possess spins, and we found two kinds of spin species with different doping levels. The ESR results indicate the itinerant features down to 170 K. The H-1 T-1(-1) for the heavy-iodine-doped HBC nanotubes follows T-0.5 and exhibits a characteristic frequency dependence. We propose that the spin excitation propagates along the one-dimensional helical chain.

DOI： 10.1143/JPSJ.77.034710

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Multi-frequency ESR measurements using X- (9.5 GHz), Q- (34 GHz), and W-band (95 GHz) microwaves, magnetic measurement using SQUID and energy band calculation were carried out on zeta-(BEDT-TTF)(2)PF6(THF) and gamma(BEDT-TTF)(2)PF6. The temperature dependence of the spin susceptibility of the two salts shows that of typical paramagnetic insulators with low-dimensional antiferromagnetic interaction. The macroscopic magnetic behaviors are apparently similar to each other, and the absolute values of the intra-chain antiferromagnetic interaction, J(intra)/k(B) of the two salts are also close to each other. However, their ground states and microscopic behaviors indicate obvious difference. (BEDT-TTF)(2)PF6(THF) undergoes an antiferromagnetic transition at around 5 K, whereas gamma-(BEDT-TTF)(2)PF6 shows no magnetic long-range ordering down to 4 K. The ESR linewidth, Delta Hpp, of zeta-(BEDT-TTF)(2)PF6(THF) was almost temperature independent in the paramagnetic region. On the other hand, the Delta H-pp of gamma-(BEDT-TTF)(2)PF6 gradually decreased as the temperature was decreased. The low-temperature electronic states of these salts are discussed in the aspect of the magnetic dimensionality.

DOI： 10.1246/bcsj.81.84

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A novel trimacrocyclic arylamine was found to be accessible to the different spin-states by consecutive electrochemical or chemical oxidation.

DOI： 10.1039/b816311a

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A fully dianisylaminophenylated aza[1(4)] metacyclophane has been synthesized that exhibits four reversible two-electron oxidation processes, and its dicationic and tetracationic species have been found to be in spin-triplet and spin-quintet states.

DOI： 10.1039/b805333b

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DOI： 10.1002/anie.200804570

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Pulsed electron nuclear double resonance (ENDOR) spin technology has been invoked for realization of a quantum computer (QC). Sample preparation of molecular spins, quantum operations, and measurements have been performed successfully, showing that ENDOR QC is feasible. We have employed a typical stable organic open-shell entity, malonyl radical, for pulsed ENDOR-based QC experiments. Time proportional phase incrementation (TPPI) technique was applied in order to characterize entangled states. The appearance of the entanglement between electron and nuclear spins was discussed based on the pulsed ENDOR-QC experiments with the TPPI detection. The generated entangled state was operated by both the microwave and RF pulses, demonstrating the appearance of a spinor property with four-pi periodicity due to electron spin-1/2, in a straightforward manner for the first time. Interconversion from one entangled state to the other one via quantum operation was demonstrated. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physe.2007.06.031

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The polaron dynamics has been investigated through the X- and Q-band ESR measurements for two types of iodine-doped long oligothiophenes, the 20-mer with octyl substituents (o-20T) and the 16-mer with hexyl substituents (h-16T). o-20T, used as a model compound of conjugated polymers with crystalline grains, gives anisotropic ESR spectra attributed to g anisotropy at low temperatures. The anisotropic spectra are found to be brought by polarons moving within the crystalline grains consisting of parallel chains. The anisotropy is shown to decrease with increasing temperature. This provides definite evidence that the polarons transfer among some grains by the assist of temperature. In contrast, h-16T, used as a model of the polymers with amorphous morphology, gives almost isotropic ESR spectra even in the Q-band measurement. This feature of h-16T is explained to be caused by a rapid interchain transfer of polarons. Spectral simulations performed for obtained spectra reveal that the ESR linewidth in the Q-band measurement is larger than that in the X band for both oligothiophenes. The difference of the linewidth is analyzed by a simplified motional narrowing model in order to draw the information of polaron dynamics. Analyses for o-20T show that the intergrain motion almost follows the variable range hopping model. The interchain motion in h-16T is found to have a much weaker temperature dependence than the intergrain motion in o-20T. This result suggests that the interchain dynamics of h-16T revealed by the ESR technique includes a variety of processes of motion.

DOI： 10.1103/PhysRevB.76.155205

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C-13 nuclear magnetic resonance (NMR) investigations were carried out for a one-dimensional organic conductor, (TMTTF)(2)PF6, to determine the charge dynamics and configuration in the proximity of the spin-Peierls phase-transition temperature, T-sP. Although no obvious NMR line splitting associated with the charge-ordering transitions in the intermediate paramagnetic states was observed, the charge separation amplitude was estimated to be rho co similar to 0.14 using the C-13 NMR spin-lattice relaxation rates for the distinct lines. The abrupt decrease in the NMR linewidth below 25 K and the small anisotropy of the NMR linewidth in the spin-Peierls phase indicate the possible redistribution of the charge separation in the proximity of T-sP. The low-temperature electronic states of (TMTTF)(2)PF6 are discussed from a microscopic point of view.

DOI： 10.1143/JPSJ.76.064715

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The electronic states of M-DNA doped with M = Mg, Ca, Zn, Mn, Fe are investigated mainly with magnetic properties. In the "wet" condition the Mn ions of Mn-DNA form a 1-D chain in the center of a DNA double helix, as evidenced from the formation of the unnatural base pair combination with M, poly(dA)-M-poly(dC), but in the "dry" condition they form a 3-D network with the antiferromagnetic ground state around 0.4 K with the superexchange coupling via water molecules. The valence of 3+ is found only in Fe-DNA, from which the base pi-band obtains pi charge carriers.

DOI： 10.1143/JPSJ.76.043801

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DOI： 10.1002/anie.200604882

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We show a new approach to manipulating the through-space spin-spin interaction by utilizing the confined cavity of a self-assembled M6L4 coordination cage. The coordination cage readily encapsulates stable organic radicals in solution, which brings the spin centers of the radicals closer to each other. In sharp contrast to the fact that the radical in solution in the absence of the cage is in a doublet state, in the presence of the cage through-space spin-spin interaction is induced through cage-encapsulation effects in solution as well as in the solid state, resulting in the triplet state of the complex. These results were confirmed by ESR spectroscopy and X-ray crystallography. The quantity of triplet species generated by encapsulation in the cage increases with increasing affinity of the radicals to the cage. We estimated the affinity between several types of guests and the cage in solution by cyclic voltammetry. We also demonstrate that the through-space interaction of organic radicals within the self-assembled coordination cage can be controlled by external stimuli such as heat or pH.

DOI： 10.1002/asia.200600293

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DOI： 10.1021/ja062654z

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The multiline signal from the S-2-state manganese cluster in the oxygen evolving complex of photosystem II (PSII) was observed in single crystals of a thermophilic cyanobacterium Thermosynechococcus Vulcanus for the first time by W-band (94 GHz) electron paramagnetic resonance (EPR). At W- band, spectra were characterized by the g-anisotropy, which enabled the precise determination of the tensor. Distinct hyperfine splittings (hfs's) as seen in frozen solutions of PSII at X-band (9.5 GHz) were detected in most of the crystal orientations relative to the magnetic field. In some orientations, however, the hfs's disappeared due to overlapping of a large number of EPR lines from eight crystallographic symmetry-related sites of the manganese cluster within the unit cell of the crystal. Analysis of the orientation-dependent spectral features yielded the following g-tensor components: g(x) = 1.988, g(y) = 1.981, g(z) = 1.965. The principal values suggested an approximate axial symmetry around the Mn(III) ion in the cluster.

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beta'-(BEDT-TTF)(TCNQ) is a compound of BEDT-TTF (=ET) and TCNQ molecules aligned orthogonally with each other, forming two-dimensional sheets and one-dimensional columns of 114-filled pi band, respectively. It is known that the metal-insulator transition occurs at 330 K at ambient pressure. We have measured the electronic spin susceptibility by means of the EPR-NMR method at 50 MHz, and the angular dependence of g-factor and line width of EPR both at Q (34 GHz) and W (94 GHz) band. We successfully confirmed that the antiferromagnetic transition occurs in ET sheets and TCNQ columns, independently.

DOI： 10.1007/s10909-006-9198-4

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The quarter-filled pi band systems, (DMc-DCNQI)(2)M(M = Li1-xCux(x <= 0.14), Ag) were systematically studied with electron paramagnetic resonance (EPR). The intercolumn spin hopping rate D-perpendicular to in Li1-xCux-salt was obtained from the EPR linewidth. The temperature dependence of D, can be understood with the hole soliton model which also explains the DC conductivity. The pi - d mixing of the Cu-salt enhances both D-perpendicular to and sigma(perpendicular to) by 10(3) times more than the Li-salt, which is consistent with the fact that the only Cu-salt has three-dimensional Fermi surface, but that Ag-salt is one-dimensional in spite of the mixing enhancement of D-perpendicular to by 10 times more than the Li-salt.

DOI： 10.1007/s10909-006-9103-1

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C-13 NMR measurements were performed for one-dimensional organic conductors, (TMTTF)(2)ReO4. An intermediate charge-ordering (CO) phase has been found firstly for a TMTTF salt with a Td-symmetry counter anion: The NMR parameters indicate two inequivalent molecules with unequal electron densities below 225 K. Moreover, the spin-singlet transition associated with ReO4 anion ordering was confirmed at around 158 K by C-13 NMR measurements. A drastic change of NMR parameters below 158 K also indicates a redistribution of the electronic charge at the anion ordering temperature.

DOI： 10.1007/s10909-006-9105-z

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13C NMR measurements were performed for a one-dimensional organic conductor, (TMTTF) 2ReO 4. The existence of an intermediate charge ordering (CO) phase was clarified for a TMTTF salt with a T d symmetry counter anion by the 13C NMR absorption line and spin-lattice relaxation rate, 13C T 1 -1. The 13C NMR spectra, which are characteristic of nuclei in equivalent molecules at room temperature, indicated two inequivalent molecules with unequal electron densities below 225 K. Moreover, the spin-singlet transition associated with ReO 4 anion ordering was confirmed at around 158K by 13C NMR. The 13C NMR lines show a marked change at 158 K. The possible redistribution of the electronic charge at the anion ordering temperature as well as the origin of the charge ordering phenomena are discussed. ©2006 The Physical Society of Japan.

DOI： 10.1143/JPSJ.75.013707

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ESR, NMR and X-ray measurements were performed for pristine and fully perdeuterio-TMTTF, TMTTF-d12 salts. Significant enhancement by deuteration of the charge-order phase transition temperature, TCO, was observed in ESR measurements for all (TMTTF)2X salts measured. No obvious relation between the SbF6 anion motion and the TMTTF charge-order was found by 19F NMR. We also performed single crystal X-ray measurements to understand the deuteration effects and temperature dependence of the crystal structure. A possible relationship between the T CO's and crystallographical parameters is proposed. The deuteration effects and possible origin of the charge-ordering transition of TMTTF salts are discussed. ©2005 The Physical Society of Japan.

DOI： 10.1143/JPSJ.74.3288

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Language：English   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

Pulsed Electron Nuclear DOuble Resonance (pulsed ENDOR) has been studied for realization of quantum algorithms, emphasizing the implementation of organic molecular entities with an electron spin and a nuclear spin for quantum information processing. The scheme has been examined in terms of quantum information processing. Particularly, superdense coding has been implemented from the experimental side and the preliminary results are represented as theoretical expectations.

DOI： 10.1142/S0219749905001377

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Language：English   Publisher：IOP PUBLISHING LTD  

From dielectric permittivity measurements, we show that deuteration yields a large increase of the transition temperature for the charge ordered state of (TMTTF)(2)X (X = AsF6, SbF6, ReO4) salts. We propose an explanation of this phenomenon, suggesting that deuteration induces a modification of the (TMTTF)(2)X crystal unit cell.

DOI： 10.1088/0953-8984/17/41/L01

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200501943

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Language：English   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja046102x

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Language：English   Publisher：AMER CHEMICAL SOC  

In this work, the cage structure of a family of europium metallofullerenes, Eu@C-74 and three isomers of Eu@C-82, were investigated. The analogy of the electronic states of three isomers of Eu@C-82 with those of three isomers of Ca@C-82 was confirmed by UV-vis-near-IR absorption spectra. The symmetries C-s, C-2, and C-2, were assigned for three isomers of Eu@C-82 by comparing each corresponding isomer of Ca@C-82. The D-3h cage structure of Eu@C-74, which is expected only for the C-74 from the isolated pentagon rule, was also confirmed by comparing its photoabsorption spectrum with that of Ca@C-74. Multifrequency electron paramagnetic resonance (EPR) spectroscopy was employed to determine the zero-field splitting (ZFS) parameters of the metallofullerenes, which are closely related to the surrounding cage structures. The experimental X- and W-band EPR spectra were completely reproduced by computer simulations based on a spin Hamiltonian considering the ZFS terms up to fourth order. The introduction of the fourth-order ZFS terms into the Hamiltonian resulted in a precise determination of the second-order ZFS terms. A nonvanishing rhombicity parameter E of Eu@C-74 demonstrated the reduction of the symmetry from D-3h to C-2nu due to the positioning of Eu2+ ion at the off-center of C-74 cage. Moreover, in this work, the semiphenomenological superposition-exchange model (SPEM) was invoked to examine a relationship between the molecular structures and ZFS parameters. All of the experimental ZFS parameters were satisfactory reproduced in terms of the SPEM, leading to confirmation of the molecular symmetries. The semiphenomenological analysis also enabled us to select the most appropriate cage for Eu@C-82 with C-2 symmetry from among three possible isomers.

DOI： 10.1021/jp031350l

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Language：English   Publisher：AMER CHEMICAL SOC  

The first exhaustive purification and characterization of the much-studied "fullerenols", prepared by reaction of C-60 in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammonium hydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simply polyhydroxylated C-60 but rather is a structurally and electronically complex C-60) radical anion with a molecular formula of Na-n(+)[C60Ox(OH)(y)](n-) (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical, preparations. Surprisingly, Na+-fullerenol is paramagnetic, exhibiting mu(B) values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R, proton relaxivities of 0.55-0.77 mM(-1)s(-l) at 20 MHz and 40 degreesC, values both slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2D nutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na+-fullerenol is mainly S = 1/2 with a minor, but significant, component of S = 1. Thus, this is the first report to characterize these widely studied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na+-fullerenol radical is likely due to a highly derivatized C60 surface that protects a cyclopentadienyl radical center on the fullerene.

DOI： 10.1021/ja047593o

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：English   Publisher：ELSEVIER SCIENCE BV  

(DMe-DCNQI)(2)M (M = Li, Ag) is a 1/4-filled spin-Peierls system. We study the spin/charge dynamics in the insulating state by EPR. The linewidth shows exponential dependence at T much greater than T-sp. Further, pressure enhances mainly prefactor of the exponential dependences. These results are successfully understood in terms of the relaxation accompanied with the intercolumn hopping caused by the spin-orbit interaction both for the Li and Ag salts. This is consistent with the scenario that the hole and spin solitons help the intercolumn charge and spin transports. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.12.1223

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：English   Publisher：ELSEVIER SCIENCE BV  

The thin films of Fe4N which were prepared by atmospheric pressure halide vapor phase deposition, were epitaxially grown on a MgO(100) substrate and have cubic structure with good crystallinity. The magnetic characteristics of Fe4N epitaxial film show soft magnetic behavior under various temperatures and various external magnetic field directions. As the temperature is decreased, the saturation magnetization increases. Also, the magnetized behavior is observed when the magnetic field is applied parallel to the film plane. It was found that the magnetic moments of Fe4N epitaxial film are facing parallel to the film plane. (C) 2003 Elsevier SAS. All rights reserved.

DOI： 10.1016/j.solidstatesciences.2003.11.004

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：OXFORD UNIV PRESS  

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Language：English   Publisher：AMER CHEMICAL SOC  

This work discusses an issue caused by omitting the fourth-order zero-field splitting (ZFS) terms in the analysis of random-orientation EPR spectra. Eu(II)-doped strontium aluminates were employed as a model system of the S-state lanthanoid ions, which have relatively large second-rank ZFS components, comparable to the conventional X-band microwave energy. The initial estimation of second- and fourth-rank ZFS components was acquired uniquely from the W-band spectrum based on a perturbation treatment of the spin Hamiltonian, and they were refined by a hybrid-eigenfield simulation approach. A parallel simulation of the X- and W-band spectra with the refined parameters reasonably reproduced both the observed spectra. The reliability of the parameters was also verified by reproducing the off-principal-axis extra lines arising from the M-S = 1/2 <----> 1/2 transition observed in the W-band spectrum. By comparison with an analysis based on the spin Hamiltonian omitting the fourth-order terms, it was concluded that omitting these terms results in an erroneous determination of the rhombic parameter (E) of the second-rank ZFS tensor. The obtained reliable second-rank ZFS tensors enabled us to invoke the superposition model, determining their principal-axis orientation. This is the first report of such relative orientation determined for Eu(II)-doped strontium aluminates.

DOI： 10.1021/jp030819

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Language：English   Publisher：AMER CHEMICAL SOC  

The spin state of the major isomer of Gd@C-82 (Gd@C-82-I) was determined by the combined use of a high-field electron spin resonance (ESR) spectrometer (W-band) and a conventional spectrometer (X-band). The ground spin state of Gd@C-82-I is characterized by an integer spin quantum number of S = 3. The spin (S = 1/2) on the pi orbital of the fullerene cage is coupled with the octet spin (S = 7/2) of the encapsulated gadolinium. in an antiferromagnetic manner with the exchange coupling constant of J = -1.8 cm(-1). In a condensed solution and solid powder, the Gd@C-82-I molecules easily formed dimers. The radical spins on the cage are canceled upon dimerization, and the resultant spin state of the dimer is described by two independent octet (S = 7/2) spins of the gadolinium. The X- and W-band ESR spectra for Gd@C-82-I are completely reproduced by an eigenfield method simulation, and ESR parameters for the g tensor, zero-field splitting tensor, and the intramolecular exchange coupling constant, J, have been determined. From the temperature dependence of the W-band ESR spectrum, the sign of the zero-field splitting constant D has been determined to be positive.

DOI： 10.1021/jp035947c

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Language：English   Publisher：ELECTROCHEMICAL SOC INC  

Epitaxially grown Fe4N thin film on a MgO(001) substrate has been examined by high-field ferromagnetic resonance (FMR) spectroscopy. When the magnetic field was applied parallel (along the in-plane [100] direction) and perpendicular to the substrate, the resonance appeared at 2.4 and 4.9 T at 94 GHz, respectively. The g-value and the effective magnetization were estimated to be 2.13 and 191 emu g(-1), respectively, using the relation derived from the Landau-Lifshitz equation of motion. Superconducting quantum interference device (SQUID) measurements also showed that the Fe4N epitaxial film has a large magnetization anisotropy, supporting that the magnetic moments lie along the in-plane direction. (C) 2003 The Electrochemical Society.

DOI： 10.1149/1.1603973

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：English   Publisher：AMER CHEMICAL SOC  

Regloselectivity of the oxidative coupling of 5,10,15-triarylporphyrin metal complexes with DDQ-Sc(OTf)(3) was dependent on the central metal and meso-aryl substituent. Oxo-quinoidal porphyrin was obtained from Ni(II) porphyrin under the same conditions.

DOI： 10.1021/ol0344826

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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We examined the dynamical magnetic properties of microstructured ferromagnetic thin films with low-dimensional superlattice structure by ferromagnetic resonance (FMR) spectroscopy. The superlattice is composed of one- or two-dimensional arrays of `islands' of permalloy on micron scale. The conventional standing spin wave (SSW) model couldn't reproduce the angular variation of the observed FMR spectra. We analyzed the observed FMR spectra by the dipolar spin wave (dipolar SW) model describing collective motion of gigantic magnetic moments, which are defined by a whole magnetization of the semimacroscopic-scale `island'. From the analysis of the observed angular variation, the dispersion relation for the dipolar SW was found to be the general formulation for the dynamical magnetic properties of the semimacroscopic systems. It was found from the analysis of the distance dependence of the inter-island magnetic interactions that the size and the shape of the ferromagnetic islands are not negligible in the dipolar SW.

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Language：Japanese   Publisher：The Magnetics Society of Japan  

Recently, unique multiple microwave absorption has been observed in ferromagnetic Ni₈₀Fe₂₀ wire arrays with lateral periodicity. As the origin of this phenomenon, we have proposed the excitation of dipolar standing waves arising from a novel collective motion of giant magnetic moments. In the present study, the dependence of the microwave absorption characteristics on the wire spacing, width, and number of wires was investigated to confirm our model. The intensity of the absorption with higher wave number decreased as wire spacing increased. Complex spectra were observed in arrays with wider wires, suggesting an overlap of main and multiple absorption. No change was obtained in the microwave absorption characteristics when the number of wires was varied between 50 and 500. These results imply the validity of the dipolar standing wave model.

DOI： 10.3379/jmsjmag.23.1125

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Language：Japanese   Publisher：The Magnetics Society of Japan  

Recently, unique multiple microwave absorption has been observed in ferromagnetic Ni₈₀Fe₂₀ wire arrays with lateral periodicity. As the origin of this phenomenon, we have proposed the excitation of dipolar standing waves arising from a novel collective motion of giant magnetic moments. In the present study, the dependence of the microwave absorption characteristics on the wire spacing, width, and number of wires was investigated to confirm our model. The intensity of the absorption with higher wave number decreased as wire spacing increased. Complex spectra were observed in arrays with wider wires, suggesting an overlap of main and multiple absorption. No change was obtained in the microwave absorption characteristics when the number of wires was varied between 50 and 500. These results imply the validity of the dipolar standing wave model.

DOI： 10.3379/jmsjmag.23.1125

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