Faculty Profiles - FURUKAWA Ko

Papers - FURUKAWA Ko

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Stable Face-to-Face Singlet Diradicaloids: Triply Linked Corrole Dimer Gallium(III) Complexes with Two μ -Hydroxo-Bridges Reviewed

Shota Ooi, Daiki Shimizu, Ko Furukawa, Takayuki Tanaka, Atsuhiro Osuka

Angewandte Chemie 130 ( 45 ) 15132 2018.11

Mixed valence salts based on carbon-centered neutral radical crystals Reviewed

T. Murata, C. Yamada, K. Furukawa, Y. Morita

Commun. Chem. 1 47 2018.9

Crystalline functionalized endohedral C-60 metallofullerides Reviewed

Ayano Nakagawa, Makiko Nishino, Hiroyuki Niwa, Katsuma Ishino, Zhiyong Wang, Haruka Omachi, Ko Furukawa, Takahisa Yamaguchi, Tatsuhisa Kato, Shunji Bandow, Jeremy Rio, Chris Ewels, Shinobu Aoyagi, Hisanori Shinohara

NATURE COMMUNICATIONS 9 3073 2018.8

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

Rational Synthesis of Antiaromatic 5,15-Dioxaporphyrin and Oxidation into β,β-Linked Dimers Reviewed

Akihide Nishiyama, Masaya Fukuda, Shigeki Mori, Ko Furukawa, Heike Fliegl, Hiroyuki Furuta, Soji Shimizu

Angewandte Chemie - International Edition 57 ( 31 ) 9728 - 9733 2018.7

Publishing type：Research paper (scientific journal)

© 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

A Stable Trimethylenemethane Triplet Diradical Based on a Trimeric Porphyrin Fused pi-System Reviewed

K. Kato, K. Furukawa, A. Osuka

Angew. Chem. Int. Ed. 57 ( 30 ) 9491 - 9494 2018.7

Redox switchable 19 pi and 18 pi 5,10,20-triaryl-5,15-diazaporphyrinoid-nickel(II) complexes Reviewed

K. Sudoh, T. Hatakeyama, K. Furukawa, H. Nakano, Y. Matano

J. Porphyrins and Phthalocyanines 22 ( 7 ) 542 - 551 2018.7

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

Metalation Control of Open-Shell Character in meso-meso Linked Porphyrin meso-Oxy Radical Dimers Reviewed

Yuta Jun-i, Norihito Fukui, Ko Furukawa, Atsuhiro Osuka

Chemistry - A European Journal 24 ( 7 ) 1528 - 1532 2018.2

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

Porphyrin-Based Air-Stable Helical Radicals Reviewed

Kenichi Kato, Ko Furukawa, Tadashi Mori, Atsuhiro Osuka

Chemistry - A European Journal 24 ( 3 ) 572 - 575 2018.1

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

Programmable arrangement of metal ions in a cofacially stacked assembly of porphyrinoids toward molecular tags Reviewed

Nozomi Mihara, Yasuyuki Yamada, Ko Furukawa, Tatsuhisa Kato, Kentaro Tanaka

Dalton Transactions 47 ( 20 ) 7044 - 7049 2018

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

Bis-Copper(II)/π-Radical Multi-Heterospin System with Non-innocent Doubly N-Confused Dioxohexaphyrin(1.1.1.1.1.0) Ligand Reviewed

Kazuhisa Yamasumi, Keiichi Nishimura, Yutaka Hisamune, Yusuke Nagae, Tomoki Uchiyama, Kazutaka Kamitani, Tomoyasu Hirai, Maiko Nishibori, Shigeki Mori, Satoru Karasawa, Tatsuhisa Kato, Ko Furukawa, Masatoshi Ishida, Hiroyuki Furuta

Chemistry - A European Journal 23 ( 61 ) 15322 - 15326 2017.11

Publishing type：Research paper (scientific journal)

© 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

Syntheses, Properties, and Catalytic Activities of Metal(II) Complexes and Free Bases of Redox-Switchable 20 pi, 19 pi, and 18 pi 5,10,15,20-Tetraaryl-5,15-diazaporphyrinoids Reviewed

Keisuke Sudoh, Takaharu Satoh, Toru Amaya, Ko Furukawa, Mao Minoura, Haruyuki Nakano, Yoshihiro Matano

CHEMISTRY-A EUROPEAN JOURNAL 23 ( 64 ) 16364 - 16373 2017.11

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

Thienylquinonoidal Porphyrins and Hexaphyrins with Singlet Diradical Ground States Reviewed

Koji Naoda, Daiki Shimizu, Jun Oh Kim, Ko Furukawa, Dongho Kim, Atsuhiro Osuka

CHEMISTRY-A EUROPEAN JOURNAL 23 ( 37 ) 8969 - 8979 2017.7

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

Stable Subporphyrin meso-Aminyl Radicals without Resonance Stabilization by a Neighboring Heteroatom Reviewed

Daiki Shimizu, Ko Furukawa, Atsuhiro Osuka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 56 ( 26 ) 7435 - 7439 2017.6

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

Fullerene C-70 as a Nanoflask that Reveals the Chemical Reactivity of Atomic Nitrogen Reviewed

Yuta Morinaka, Rui Zhang, Satoru Sato, Hidefumi Nikawa, Tatsuhisa Kato, Ko Furukawa, Michio Yamada, Yutaka Maeda, Michihisa Murata, Atsushi Wakamiya, Shigeru Nagase, Takeshi Akasaka, Yasujiro Murata

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 56 ( 23 ) 6488 - 6491 2017.6

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

Stable Ni-II Porphyrin meso-Oxy Radical with a Quartet Ground State Reviewed

Cosima Staehler, Daiki Shimizu, Kota Yoshida, Ko Furukawa, Rainer Herges, Atsuhiro Osuka

CHEMISTRY-A EUROPEAN JOURNAL 23 ( 30 ) 7217 - 7220 2017.5

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

Design and Synthesis of a Caged Carboxylic Acid with a Donor-pi-Donor Coumarin Structure: One-photon and Two-photon Uncaging Reactions Using Visible and Near-Infrared Lights Reviewed

Youhei Chitose, Manabu Abe, Ko Furukawa, Jhe-Yi Ling, Tzu-Chau Lin, Claudine Katan

ORGANIC LETTERS 19 ( 10 ) 2622 - 2625 2017.5

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

Oxidation of allenes bearing 1,8-diphenoxy or diaryloxyacridene moieties Reviewed

Shin-ichi Fuku-en, Junki Yamamoto, Ko Furukawa, Daisuke Hashizume, Naomi Kawata, Yohsuke Yamamoto

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY 30 ( 4 ) e3665 2017.4

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

Nitrogen-Bridged Metallodiazaporphyrin Dimers: Synergistic Effects of Nitrogen Bridges and meso-Nitrogen Atoms on Structure and Properties Reviewed

Masahiro Kawamata, Takuma Sugai, Mao Minoura, Yasuhisa Maruyama, Ko Furukawa, Cole Holstrom, Victor N. Nemykin, Haruyuki Nakano, Yoshihiro Matano

CHEMISTRY-AN ASIAN JOURNAL 12 ( 7 ) 816 - 821 2017.4

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

Highly planar diarylamine-fused porphyrins and their remarkably stable radical cations Reviewed

Norihito Fukui, Wonhee Cha, Daiki Shimizu, Juwon Oh, Ko Furukawa, Hideki Yorimitsu, Dongho Kim, Atsuhiro Osuka

CHEMICAL SCIENCE 8 ( 1 ) 189 - 199 2017.1

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

Syntheses, Properties, and Catalytic Activities of Metal(II) Complexes and Free Bases of Redox-Switchable 20π, 19π, and 18π 5,10,15,20-Tetraaryl-5,15-diazaporphyrinoids Reviewed International journal

Keisuke Sudoh, Takaharu Satoh, Toru Amaya, Ko Furukawa, Mao Minoura, Haruyuki Nakano, Yoshihiro Matano

Chemistry-A European Journal 23 ( 64 ) 16364 - 16373 2017

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

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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