Faculty Profiles - FURUKAWA Ko

Papers - FURUKAWA Ko

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Intermolecular Toroidal Conjugation: Circularly Stacked 16 π-Planes Formed by Supramolecular Assembly Enabling Cyclic Charge and Energy Delocalization

Daisuke Sakamaki, Koki Tsubono, Minami Nakamura, Daiki Shimizu, Yasunori Matsui, Hiroshi Ikeda, Ko Furukawa, Hideki Fujiwara

2025.2

Publisher：American Chemical Society (ACS)

Toroidal conjugation is a unique way of charge and exciton delocalization via through-space overlap among circularly stacked π-orbitals, but the examples have been limited to intramolecular phenomena where π-planes are arranged around a hub molecule. In this study, we extend this concept to intermolecular phenomena and demonstrate the first example of intermolecular toroidal conjugation in designed systems, in which a circular π-stacked array is formed by molecular self-assembly. X-ray single-crystal analysis unequivocally revealed a toroidal array of 16 π-planes formed by the supramolecular dimerization of phthalocyanines substituted with eight pillar-like diazapentacenes interdigitating their π-pillars. The experimentally determined interplanar distances in the toroidal π-stacking array were close enough to realize through-space conjugation. We investigated the existence of charge and exciton delocalization in the toroidal π-stacking array using various steady-state and time-resolved spectroscopies and found that the positive charge migrated in the toroidal π-stacking array in the cationic and photoexcited states.

DOI： 10.26434/chemrxiv-2025-hnn6b-v2

Two Approaches to the Synthesis of Redox‐Switchable 5,10,20‐Triaryl‐5,15‐diazaporphyrinoids

Yui Murata, Keisuke Sudoh, Ko Furukawa, Haruyuki Nakano, Yoshihiro Matano

Chemistry – An Asian Journal 2025.2

π‐Expansion on a Polycyclic Stable Neutral Radical: Synthesis and Physical Properties of a Benz‐Annulated Trioxotriangulene

Tsuyoshi Murata, Satsuki Doi, Rina Ishikawa, Ko Furukawa, Yasushi Morita

Asian Journal of Organic Chemistry 14 ( 3 ) 2024.12

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

Abstract

We report the synthesis of a benz‐annulated derivative of trioxotriangulene (TOT), a fused polycyclic organic neutral radical, and also the investigation on the electronic effects of π‐expansion. The neutral radical species was highly stable under air in both solution and solid states. Quantum chemical calculation suggested that the molecule has a completely planar molecular structure, and the electronic spin is widely delocalized throughout the π‐skeleton while maintaining three‐fold symmetry, which was experimentally supported by electronic spin resonance spectrum. The neutral radical also showed a strong π‐association ability comparable to that of TOT neutral radical derivatives.

DOI： 10.1002/ajoc.202400690

Spin–spin interaction in a highly stable neutral diradical: σ-boned dimer of trioxotriangulene

Tsuyoshi Murata, Shusaku Ukai, Sawa Yamaguchi, Ko Furukawa, Yasushi Morita

Chemistry Letters 53 ( 2 ) 2024.2

Publishing type：Research paper (scientific journal) Publisher：Oxford University Press (OUP)

Abstract

A σ-bonded dimer of 4,8,10-trioxotriangulene (TOT) was newly synthesized and its electronic spin structure was characterized. The neutral diradical had a singlet ground state due to the strong antiferromagnetic interaction through the σ-bond. The strong intramolecular interaction within the σ-dimer caused a near-infrared photoabsorption of around 700–1,000 nm, which is close to that of the π-stacked dimer of TOT monoradical.

DOI： 10.1093/chemle/upae030

Other Link： https://academic.oup.com/chemlett/article-pdf/53/2/upae030/56760582/upae030.pdf

Improved Synthesis of Free Bases of 5,10,15,20-Tetraaryl-5,15-diazaporphyrinoid for Conversion to Silicon(IV) Complexes

Hiroya Suzuki, Ko Furukawa, Mao Minoura, Haruyuki Nakano, Yoshihiro Matano

Bulletin of the Chemical Society of Japan 2023.12

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

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

DOI： 10.1093/bulcsj/uoad022

Selective hetero-bis-metalation of a <i>cisoid</i> isomer of doubly N-confused dioxohexaphyrin

Keito Shimomura, Yuma Nakamura, Hiroto Kai, Kyosuke Saito, Ko Furukawa, Shigeki Mori, Masatoshi Ishida, Hiroyuki Furuta

Journal of Porphyrins and Phthalocyanines 26 ( 12 ) A - H 2022.10

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

Novel site-selective hetero-copper(II)/zinc(II) complexes of a cisoid-configured doubly N-confused dioxohexaphyrin analog (c-ZnCu-2 and c-CuZn-2) were synthesized and characterized. The resulting heterometal complexes exhibited a unique near-infrared (NIR) absorption feature, and the facile redox-active properties originated from the large 26[Formula: see text]-conjugated structure. The distinct difference between the site-dependent c-ZnCu-2 and c-CuZn-2appeared in the specific structural parameters of the d<sup>9</sup> copper centers in the electron paramagnetic resonance spectra and the Lewis acidity of the zinc centers upon the base-titrations. These complexes have potential for the hetero-metal-containing [Formula: see text]-material applications that respond to the NIR light.

DOI： 10.1142/s1088424622500456

Synthesis, Electrochemical Behavior, and Catalytic Activity of Cobalt Complexes of 5,10,15,20-Tetraaryl-5,15-diazaporphyrinoids

Yuna Satoh, Yuta Kudoh, Ko Furukawa, Yoshihiro Matano

Organic Letters 24 ( 21 ) 3839 - 3843 2022.6

Synthesis, Optical Properties, and Electrochemical Behavior of 5,10,15,20-Tetraaryl-5,15-diazaporphyrin-Amine Hybrids

Yuna Satoh, Yutaro Fujita, Naoya Muramatsu, Ko Furukawa, Tadaaki Ikoma, Mao Minoura, Haruyuki Nakano, Yoshihiro Matano

CHEMPLUSCHEM 86 ( 10 ) 1476 - 1486 2021.10

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

This work reports a series of covalently linked hybrids comprising 5,10,15,20-tetraaryl-5,15-diazaporphyrinoids (M-TADAP; M = Ni, Zn, Cu) and amines. M-TADAP-amine hybrids were prepared via the metal-templated cyclization of the corresponding metal(II)-dipyrrin complexes and redox reactions on the DAP unit. In the UV/vis/near-IR absorption spectra of the hybrids containing an 18 pi-electron DAP ring, broad charge-transfer bands were observed, reflecting the electron-donating property of the para-aminophenyl groups and the electron-accepting property of the 18 pi TADAP dication. The electrochemical behavior of the M-TADAP-amine hybrids was strongly dependent on the structure of the peripheral amine units. Further electrochemical oxidation of the hybrids bearing N-Ph groups conceivably generated amine-centered radicals, which sequentially underwent irreversible coupling to form benzidine-linked M-TADAP polymer films. The Ni-TADAP-benzidine polymer exhibited the electric conductivity of 2x10(-3) S m(-1).

DOI： 10.1002/cplu.202100429

Chiral Interlocked Corrole Dimers Directly Linked at Inner Carbon Atoms of Confused Pyrrole Rings

Yogesh Kumar Maurya, Pingchun Wei, Takahide Shimada, Kazuhisa Yamasumi, Shigeki Mori, Ko Furukawa, Hajime Kusaba, Tatsumi Ishihara, Yongshu Xie, Masatoshi Ishida, Hiroyuki Furuta

Chemistry – An Asian Journal 16 ( 7 ) 743 - 747 2021.4

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

A facile synthetic strategy towards conformationally stable chiral chromophores based on dimeric porphyrinoids has been established. A peculiar class of face-to-face intramolecularly interlocked corrole dimers were formed by the oxidative C−C coupling linked at the inner carbon sites upon simple treatment of copper(II) ions. Their intrinsic electronic structures were modulated by the peripheral corrole ring annulations, which lead to distinct optical properties and redox profiles. The stereogenic carbon centers implemented in the confused corrole skeleton provided a rationale for designing novel chiral materials.

DOI： 10.1002/asia.202100083

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/asia.202100083

A Robust Porphyrin‐Stabilized Triplet Carbon Diradical

Kaisheng Wang, Pingting Liu, Fenni Zhang, Ling Xu, Mingbo Zhou, Akito Nakai, Kenichi Kato, Ko Furukawa, Takayuki Tanaka, Atsuhiro Osuka, Jianxin Song

Angewandte Chemie International Edition 60 ( 13 ) 7002 - 7006 2021.3

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

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

p-Nitroterphenyl units for near-infrared two-photon uncaging of calcium ions

Thuy Thi Thu Pham, Satish Jakkampudi, Ko Furukawa, Fung Yu Cheng, Tzu Chau Lin, Yoki Nakamura, Norimitsu Morioka, Manabu Abe

Journal of Photochemistry and Photobiology A: Chemistry 409 2021.3

Publishing type：Research paper (scientific journal)

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

Doubly Strapped Redox-Switchable 5,10,15,20-Tetraaryl-5,15-diazaporphyrinoids: Promising Platforms for the Evaluation of Paratropic and Diatropic Ring-Current Effects

Hikari Ochiai, Ko Furukawa, Haruyuki Nakano, Yoshihiro Matano

Journal of Organic Chemistry 86 ( 3 ) 2283 - 2296 2021.2

Publishing type：Research paper (scientific journal)

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

TTF-Annulated Silicon Phthalocyanine Oligomers and Their External-Stimuli-Responsive Orientational Ordering

Yuta Shiina, Yuto Kage, Ko Furukawa, Heng Wang, Hirofumi Yoshikawa, Hiroyuki Furuta, Nagao Kobayashi, Soji Shimizu

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 59 ( 50 ) 22721 - 22730 2020.12

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

Synthesis and properties of hypervalent electron-rich pentacoordinate nitrogen compounds Reviewed

Chenting Yan, Masato Takeshita, Jun-ya Nakatsuji, Akihiro Kurosaki, Kaoko Sato, Rong Shang, Masaaki Nakamoto, Yohsuke Yamamoto, Yohei Adachi, Ko Furukawa, Ryohei Kishi, Masayoshi Nakano

CHEMICAL SCIENCE 11 ( 19 ) 5082 - 5088 2020.5

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

Cyclophane-Type Chlorin Dimers from Dynamic Covalent Chemistry of 2,18-Porphyrinyl Dicyanomethyl Diradicals

B. Adinarayana, Kenichi Kato, Daiki Shimizu, Takayuki Tanaka, Ko Furukawa, Atsuhiro Osuka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 59 ( 11 ) 4320 - 4323 2020.3

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

Synthesis and optical, magnetic, and electrochemical properties of 5,10,15,20-tetraaryl-5,15-diazaporphyrin - tertiary amine conjugates Reviewed

Keisuke Sudoh, Yuna Satoh, Ko Furukawa, Haruyuki Nakano, Yoshihiro Matano

JOURNAL OF PORPHYRINS AND PHTHALOCYANINES 24 ( 1-3 ) 286 - 297 2020.1

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

Stable radical versus reversible sigma-bond formation of (porphyrinyl)dicyanomethyl radicals Reviewed

Adinarayana B, Shimizu Daiki, Furukawa Ko, Osuka Atsuhiro

CHEMICAL SCIENCE 10 ( 23 ) 6007 - 6012 2019.6

Publishing type：Research paper (scientific journal)

(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

Synthesis of Redox-switchable 5,15-Dialkyl-10,20-diaryl-5,15-diazaporphyrins and Diversification of their N-Alkyl Groups Reviewed

Mutoh Mai, Sudoh Keisuke, Furukawa Ko, Minoura Mao, Nakano Haruyuki, Matano Yoshihiro

ASIAN JOURNAL OF ORGANIC CHEMISTRY 8 ( 3 ) 352 - 355 2019.3

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

Synthesis and properties of redox-switchable zinc complexes of 10,15,20-triaryl-15-aza-5-oxaporphyrin Reviewed

Sudoh Keisuke, Furukawa Ko, Nakano Haruyuki, Shimizu Soji, Matano Yoshihiro

HETEROATOM CHEMISTRY 29 ( 5-6 ) 2018.12

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

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

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

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 57 ( 45 ) 14916 - 14920 2018.11

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

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

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

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

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

Design, Synthesis, and Reaction of pi-Extended Coumarin-based New Caged Compounds with Two-photon Absorption Character in the Near-IR Region Reviewed

Youhei Chitose, Manabu Abe, Ko Furukawa, Claudine Katan

CHEMISTRY LETTERS 45 ( 10 ) 1186 - 1188 2016.10

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

Design and Synthesis of a 4-Nitrobromobenzene Derivative Bearing an Ethylene Glycol Tetraacetic Acid Unit for a New Generation of Caged Calcium Compounds with Two-Photon Absorption Properties in the Near-IR Region and Their Application in Vivo Reviewed

Satish Jakkampudi, Manabu Abe, Naomitsu Komori, Ryukichi Takagi, Ko Furukawa, Claudine Katan, Wakako Sawada, Noriko Takahashi, Haruo Kasai

ACS Omega 1 ( 2 ) 193 - 201 2016.8

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

Spontaneous Formation of an Air-Stable Radical upon the Direct Fusion of Diphenylmethane to a Triarylporphyrin Reviewed

Kenichi Kato, Wonhee Cha, Juwon Oh, Ko Furukawa, Hideki Yorimitsu, Dongho Kim, Atsuhiro Osuka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 ( 30 ) 8711 - 8714 2016.7

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

meso-to-meso Sulfide- and Disulfide-Bridged Subporphyrin Dimers Reviewed

Graeme Copley, Daiki Shimizu, Juwon Oh, Jooyoung Sung, Ko Furukawa, Dongho Kim, Atsuhiro Osuka

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 0 ( 11 ) 1977 - 1981 2016.4

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

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

Redox-Switchable 20-, 19-, and 18-Electron 5,10,15,20-Tetraaryl-5,15-diazaporphyrinoid Nickel(II) Complexes Reviewed

Takaharu Satoh, Mao Minoura, Haruyuki Nakano, Ko Furukawa, Yoshihiro Matano

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 ( 6 ) 2235 - 2238 2016.2

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

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

Isolation of Hypervalent Group-16 Radicals and Their Application in Organic-Radical Batteries Reviewed

Yasuyuki Imada, Hideyuki Nakano, Ko Furukawa, Ryohei Kishi, Masayoshi Nakano, Hitoshi Maruyama, Masaaki Nakamoto, Akira Sekiguchi, Masahiro Ogawa, Toshiaki Ohta, Yohsuke Yamamoto

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 ( 2 ) 479 - 482 2016.1

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

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

Design and synthesis of a new chromophore, 2-(4-nitrophenyl)benzofuran, for two-photon uncaging using near-IR light Reviewed

Naomitsu Komori, Satish Jakkampudi, Ryusei Motoishi, Manabu Abe, Kenji Kamada, Ko Furukawa, Claudine Katan, Wakako Sawada, Noriko Takahashi, Haruo Kasai, Bing Xue, Takayoshi Kobayashi

CHEMICAL COMMUNICATIONS 52 ( 2 ) 331 - 334 2016

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

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

Triarylporphyrin meso-Oxy Radicals: Remarkable Chemical Stabilities and Oxidation to Oxophlorin pi-Cations Reviewed

Daiki Shimizu, Juwon Oh, Ko Furukawa, Dongho Kim, Atsuhiro Osuka

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 ( 49 ) 15584 - 15594 2015.12

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

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

Microscopic evidence of a metallic state in the one-pot organic conductor ammonium tetrathiapentalene carboxylate Reviewed

Toshikazu Nakamura, Ko Furukawa, Takeshi Terauchi, Yuka Kobayashi

PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS 9 ( 8 ) 480 - 484 2015.8

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

Comparison of electronic effects of beta-aryl substituents on optical and electrochemical properties of 5,15-diazaporphyrin pi-systems Reviewed

Satoshi Omomo, Ko Furukawa, Haruyuki Nakano, Yoshihiro Matano

JOURNAL OF PORPHYRINS AND PHTHALOCYANINES 19 ( 6 ) 775 - 785 2015.6

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

Creation of Superheterojunction Polymers via Direct Polycondensation: Segregated and Bicontinuous Donor-Acceptor pi-Columnar Arrays in Covalent Organic Frameworks for Long-Lived Charge Separation Reviewed

Shangbin Jin, Mustafa Supur, Matthew Addicoat, Ko Furukawa, Long Chen, Toshikazu Nakamura, Shunichi Fukuzumi, Stephan Irle, Donglin Jiang

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 ( 24 ) 7817 - 7827 2015.6

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

meso-Hydroxysubporphyrins: A Cyclic Trimeric Assembly and a Stable meso-Oxy Radical Reviewed

Daiki Shimizu, Juwon Oh, Ko Furukawa, Dongho Kim, Atsuhiro Osuka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 54 ( 22 ) 6613 - 6617 2015.5

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

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

Lowering the Reduction Potential of a Boron Compound by Means of the Substituent Effect of the Boryl Group: One-Electron Reduction of an Unsymmetrical Diborane(4) Reviewed

Hiroki Asakawa, Ka-Ho Lee, Ko Furukawa, Zhenyang Lin, Makoto Yamashita

CHEMISTRY-A EUROPEAN JOURNAL 21 ( 11 ) 4267 - 4271 2015.3

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

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

Oxidation of an allene compound bearing 1,8-dichloroacridene moieties and photolysis of the halogenated allene compound for the generation of triplet carbenes Reviewed

Shin-ichi Fuku-en, Ko Furukawa, Takahiro Sasamori, Norihiro Tokitoh, Manabu Abe, Yohsuke Yamamoto

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY 28 ( 2 ) 79 - 87 2015.2

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

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

Optical, Electrochemical, and Magnetic Properties of Pyrrole- and Thiophene-Bridged 5,15-Diazaporphyrin Dimers Reviewed

Satoshi Omomo, Yasuhisa Maruyama, Ko Furukawa, Taniyuki Furuyama, Haruyuki Nakano, Nagao Kobayashi, Yoshihiro Matano

CHEMISTRY-A EUROPEAN JOURNAL 21 ( 5 ) 2003 - 2010 2015.1

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

A Stable Organic π-Radical of a Zinc(II)-Copper(I)-Zinc(II) Complex of Decaphyrin Reviewed

Tanaka, Y., Yoneda, T., Furukawa, K., Koide, T., Mori, H., Tanaka, T., Shinokubo, H., Osuka, A.

Angewandte Chemie - International Edition 54 ( 37 ) 10908 - 10911 2015

Phenalenyl-fused porphyrins with different ground states Reviewed

Wangdong Zeng, Sangsu Lee, Minjung Son, Masatoshi Ishida, Ko Furukawa, Pan Hu, Zhe Sun, Dongho Kim, Jishan Wu

CHEMICAL SCIENCE 6 ( 4 ) 2427 - 2433 2015

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

Acid/base-regulated reversible electron transfer disproportionation of N-N linked bicarbazole and biacridine derivatives Reviewed

Palash Pandit, Koji Yamamoto, Toshikazu Nakamura, Katsuyuki Nishimura, Yuki Kurashige, Takeshi Yanai, Go Nakamura, Shigeyuki Masaoka, Ko Furukawa, Yumi Yakiyama, Masaki Kawano, Shuhei Higashibayashi

CHEMICAL SCIENCE 6 ( 7 ) 4160 - 4173 2015

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

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

Persistent antimony- and bismuth-centered radicals in solution Reviewed

Shintaro Ishida, Fumiya Hirakawa, Ko Furukawa, Kenji Yoza, Takeaki Iwamoto

Angewandte Chemie International Edition 53 ( 42 ) 11172 - 11176 2014.7

Photoelectric Covalent Organic Frameworks: Converting Open Lattices into Ordered Donor-Acceptor Heterojunctions Reviewed

Long Chen, Ko Furukawa, Jia Gao, Atsushi Nagai, Toshikazu Nakamura, Yuping Dong, Donglin Jiang

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 ( 28 ) 9806 - 9809 2014.7

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

Covalently Linked 5,15-Diazaporphyrin Dimers: Promising Scaffolds for a Highly Conjugated Azaporphyrin pi System Reviewed

Yoshihiro Matano, Daisuke Fujii, Tarou Shibano, Ko Furukawa, Tomohiro Higashino, Haruyuki Nakano, Hiroshi Imahori

CHEMISTRY-A EUROPEAN JOURNAL 20 ( 12 ) 3342 - 3349 2014.3

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

Indolo[2,3-b]carbazoles with tunable ground states: how Clar's aromatic sextet determines the singlet biradical character Reviewed

Ding Luo, Sangsu Lee, Bin Zheng, Zhe Sun, Wangdong Zeng, Kuo-Wei Huang, Ko Furukawa, Dongho Kim, Richard D. Webster, Jishan Wu

CHEMICAL SCIENCE 5 ( 12 ) 4944 - 4952 2014

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

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

Near-IR absorbing nickel(II) porphyrinoids prepared by regioselective insertion of silylenes into antiaromatic nickel(II) norcorrole Reviewed

Fukuoka, T., Uchida, K., Sung, Y.M., Shin, J.-Y., Ishida, S., Lim, J.M., Hiroto, S., Furukawa, K., Kim, D., Iwamoto, T., Shinokubo, H.

Angewandte Chemie - International Edition 53 ( 6 ) 1506 - 1509 2014

A kinetically blocked 1,14:11,12-dibenzopentacene: a persistent triplet diradical of a non-Kekule polycyclic benzenoid hydrocarbon Reviewed

Yuan Li, Kuo-Wei Huang, Zhe Sun, Richard D. Webster, Zebing Zeng, Wangdong Zeng, Chunyan Chi, Ko Furukawa, Jishan Wu

CHEMICAL SCIENCE 5 ( 5 ) 1908 - 1914 2014

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

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

A stable metallic state of (TTPCOO)(2)NH4 with a mobile dopant Reviewed

Takeshi Terauchi, Satoshi Sumi, Yuka Kobayashi, Toshikazu Nakamura, Ko Furukawa, Yohji Misaki

CHEMICAL COMMUNICATIONS 50 ( 54 ) 7111 - 7113 2014

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

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

Redox Modulation of para-Phenylenediamine by Substituted Nitronyl Nitroxide Groups and Their Spin States Reviewed

Akihiro Ito, Ryohei Kurata, Daisuke Sakamaki, Soichiro Yano, Yosuke Kono, Yoshiaki Nakano, Ko Furukawa, Tatsuhisa Kato, Kazuyoshi Tanaka

JOURNAL OF PHYSICAL CHEMISTRY A 117 ( 48 ) 12858 - 12867 2013.12

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

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

Meta - Para -linked octaaza[18]cyclophanes and their polycationic states Reviewed

Daisuke Sakamaki, Akihiro Ito, Ko Furukawa, Tatsuhisa Kato, Kazuyoshi Tanaka

Journal of Organic Chemistry 78 ( 7 ) 2947 - 2956 2013.4

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

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

X-ray observation of a helium atom and placing a nitrogen atom inside He@C-60 and He@C-70 Reviewed

Yuta Morinaka, Satoru Sato, Atsushi Wakamiya, Hidefumi Nikawa, Naomi Mizorogi, Fumiyuki Tanabe, Michihisa Murata, Koichi Komatsu, Ko Furukawa, Tatsuhisa Kato, Shigeru Nagase, Takeshi Akasaka, Yasujiro Murata

NATURE COMMUNICATIONS 4 1554 2013.3

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

Charge Dynamics in A Donor-Acceptor Covalent Organic Framework with Periodically Ordered Bicontinuous Heterojunctions Reviewed

Shangbin Jin, Xuesong Ding, Xiao Feng, Mustafa Supur, Ko Furukawa, Seiya Takahashi, Matthew Addicoat, Mohamed E. El-Khouly, Toshikazu Nakamura, Stephan Irle, Shunichi Fukuzumi, Atsushi Nagai, Donglin Jiang

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 52 ( 7 ) 2017 - 2021 2013

Organometallic ionic liquids from alkyloctamethylferrocenium cations: thermal properties, crystal structures, and magnetic properties Reviewed

Yusuke Funasako, Takashi Inagaki, Tomoyuki Mochida, Toshihiro Sakurai, Hitoshi Ohta, Ko Furukawa, Toshikazu Nakamura

DALTON TRANSACTIONS 42 ( 23 ) 8317 - 8327 2013

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

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

Large pore donor-acceptor covalent organic frameworks Reviewed

Shangbin Jin, Ko Furukawa, Matthew Addicoat, Long Chen, Seiya Takahashi, Stephan Irle, Toshikazu Nakamura, Donglin Jiang

CHEMICAL SCIENCE 4 ( 12 ) 4505 - 4511 2013

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

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

Simultaneous Control of Carriers and Localized Spins with Light in Organic Materials Reviewed

Toshio Naito, Tomoaki Karasudani, Keishi Ohara, Takahiro Takano, Yukihiro Takahashi, Tamotsu Inabe, Ko Furukawa, Toshikazu Nakamura

ADVANCED MATERIALS 24 ( 46 ) 6153 - 6157 2012.12

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

Switchable Intermolecular Communication in a Four-Fold Rotaxane Reviewed

Y. Yamada, M. Okamoto, K. Furukawa, T. Kato, K. Tanaka

Angew. Chem. Int. Ed. 51 709 - 713 2012.1

A Polymacrocyclic Oligoarylamine with a Pseudobeltane Motif: Towards a Cylindrical Multispin System Reviewed

Daisuke Sakamaki, Akihiro Ito, Ko Furukawa, Tatsuhisa Kato, Motoo Shiro, Kazuyoshi Tanaka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 ( 51 ) 12776 - 12781 2012

Physical properties of a molecular conductor (BEDT-TTF)(2)I-3 nanohybridized with silica nanoparticles by dry grinding Reviewed

Akira Funabiki, Hiroki Sugiyama, Tomoyuki Mochida, Kunihiro Ichimura, Takashi Okubo, Ko Furukawa, Toshikazu Nakamura

RSC ADVANCES 2 ( 3 ) 1055 - 1060 2012

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

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

1,3,5-Benzenetriamine Double- and Triple-Decker Molecules Reviewed

Daisuke Sakamaki, Akihiro Ito, Kazuyoshi Tanaka, Ko Furukawa, Tatsuhisa Kato, Motoo Shiro

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 ( 33 ) 8281 - 8285 2012

13C NMR study of the magnetic properties of the quasi-one-dimensional conductor (TMTTF)2SbF6 Reviewed

F. Iwase, K. Sugiura, K. Furukawa, T. Nakamura

Physical Review B - Condensed Matter and Materials Physics 84 ( 11 ) 2011.9

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

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

C-13 NMR study of the magnetic properties of the quasi-one-dimensional conductor (TMTTF)(2)SbF6 Reviewed

F. Iwase, K. Sugiura, K. Furukawa, T. Nakamura

PHYSICAL REVIEW B 84 ( 11 ) 115140 2011.9

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

Gd-2@C79N: Isolation, Characterization, and Monoadduct Formation of a Very Stable Heterofullerene with a Magnetic Spin State of S=15/2 Reviewed

Wujun Fu, Jianyuan Zhang, Tim Fuhrer, Hunter Champion, Ko Furukawa, Tatsuhisa Kato, James E. Mahaney, Brian G. Burke, Keith A. Williams, Kenneth Walker, Caitlyn Dixon, Jiechao Ge, Chunying Shu, Kim Harich, Harry C. Dorn

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 ( 25 ) 9741 - 9750 2011.6

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

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

Ferromagnetic Spin Coupling between Endohedral Metallofullerene La@C-82 and a Cyclodimeric Copper Porphyrin upon Inclusion Reviewed

Fatin Hajjaj, Kentaro Tashiro, Hidefumi Nikawa, Naomi Mizorogi, Takeshi Akasaka, Shigeru Nagase, Ko Furukawa, Tatsuhisa Kato, Takuzo Aida

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 ( 24 ) 9290 - 9292 2011.6

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

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

Structural investigation of the spin-singlet phase in (TMTTF)2I Reviewed

Ko Furukawa, Koichi Sugiura, Fumitatsu Iwase, Toshikazu Nakamura

Physical Review B - Condensed Matter and Materials Physics 83 ( 18 ) 2011.5

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

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

Structural investigation of the spin-singlet phase in (TMTTF)(2)I Reviewed

Ko Furukawa, Koichi Sugiura, Fumitatsu Iwase, Toshikazu Nakamura

PHYSICAL REVIEW B 83 ( 18 ) 184419 2011.5

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

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

Photoinduced Triplet States of Photoconductive TTF Derivatives Including a Fluorescent Group Reviewed

Ko Furukawa, Yasuo Sugishima, Hideki Fujiwara, Toshikazu Nakamura

CHEMISTRY LETTERS 40 ( 3 ) 292 - 294 2011.3

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

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

Magnetic memory based on magnetic alignment of a paramagnetic ionic liquid near room temperature Reviewed

Yusuke Funasako, Tomoyuki Mochida, Takashi Inagaki, Takahiro Sakurai, Hitoshi Ohta, Ko Furukawa, Toshikazu Nakamura

CHEMICAL COMMUNICATIONS 47 ( 15 ) 4475 - 4477 2011

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

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

Novel Type of Career Generated System: Magnetic Investigations of TTF-Based Self-Doped Hydrogen-Bonding Conductor Reviewed

Ko Furukawa, Toshikazu Nakamura, Yuka Kobayashi, Takashi Ogura

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 ( 5 ) 053701 2010.5

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

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

Spin-Dynamics in Vicinity of Spin-Gap Phase Transition for Organic Conductor (TMTTF)(2)X Reviewed

Ko Furukawa, Toshifumi Hara, Toshikazu Nakamura

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 ( 4 ) 043702 2010.4

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

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

Submillimeter and millimeter wave ESR measurements of frustrated triangular lattice substance InMnO3 Reviewed

N. Matsumi, S. Okubo, M. Fujisawa, T. Sakurai, H. Ohta, K. Furukawa, T. Nakamura, H. Kikuchi

2009 34TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, VOLS 1 AND 2 574 - + 2009

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.

The Molecular Solid from a Viewpoint of Photo-Induced Phase Transition and Related Phenomena

NAKAMURA Toshikazu, FURUKAWA Ko

rle 36 ( 6 ) 339 - 342 2008.6

Language：Japanese Publisher：The Laser Society of Japan

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

Other Link： https://jlc.jst.go.jp/DN/JALC/00315542851?from=CiNii

Possible one-dimensional helical conductor: Hexa-peri-hexabenzocoronene nanotube Reviewed

Toshifumi Hara, Ko Furukawa, Toshikazu Nakamura, Yohei Yamamoto, Atsuko Kosaka, Wusong Jin, Takanori Fukushima, Takuzo Aida

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 3 ) 034710 2008.3

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

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

Redistribution of charge in the proximity of the spin-Peierls transition: C-13 NMR investigation of (TMTTF)(2)PF6 Reviewed

Toshikazu Nakamura, Ko Furukawa, Toshifumi Hara

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 6 ) 064715 2007.6

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

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

AF-like ground state of Mn-DNA and charge transfer from Fe to base-pi-band in Fe-DNA Reviewed

Kenji Mizoguchi, Shunsuke Tanaka, Masaya Ojima, Sayaka Sano, Mai Nagatori, Hirokazu Sakamoto, Yuki Yonezawa, Yuji Aoki, Hideyuki Sato, Kou Furukawa, Toshikazu Nakamura

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 4 ) 043801 2007.4

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

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

C-13 NMR analyses of successive charge ordering in (TMTTF)(2)ReO4 Reviewed

T Nakamura, K Furukawa, T Hara

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 75 ( 1 ) 13707 2006.1

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

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

Ferromagnetic resonance studies on Ni80Fe20 wire arrays Reviewed

A. Maeda, M. Susaki, K. Furukawa, T. Takui

INTERMAG 2006 - IEEE International Magnetics Conference 934 2006

Deuteration effect and possible origin of the charge-ordering transition of (TMTTF)(2)X Reviewed

K Furukawa, T Hara, T Nakamura

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 12 ) 3288 - 3294 2005.12

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

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

The effect of deuteration on the transition into a charge ordered state of (TMTTF)(2)X salts Reviewed

F Nad, P Monceau, T Nakamura, K Furukawa

JOURNAL OF PHYSICS-CONDENSED MATTER 17 ( 41 ) L399 - L406 2005.10

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

High frequency EPR of the Mn-cluster in single crystals of cyanobacterial photosystem II Reviewed

Asako Kawamori, Jian-Ren Shen, Hiroyuki Mino, Ko Furukawa, Hideto Matsuoka, Tatsuhisa Kato

Photosynthesis: Fundamental Aspects to Global Perspectives 406 - 408 2005

Electrochemical polymerization of terthiophene-fullerene derivative and its optical property for organic solar cells Reviewed

M Morita, K Furukawa, Y Murata, T Yamazaki, K Komatsu, N Maruyama, T Yamao, S Fujita

2005 PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS 516 - 517 2005

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.

Importance of fourth-order zero-field splitting terms in random-orientation EPR spectra of Eu(II)-doped strontium aluminate Reviewed

H Matsuoka, K Furukawa, K Sato, D Shiomi, Y Kojima, K Hirotsu, N Furuno, T Kato, T Takui

JOURNAL OF PHYSICAL CHEMISTRY A 107 ( 51 ) 11539 - 11546 2003.12

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

Pseudo-octahedral high-spin Co(II) complexes with orbitally degenerate ground states as studied by SQUID and ESR spectroscopy

H Matsuoka, T Yoshida, K Kubono, K Sato, D Shiomi, K Furukawa, T Kato, K Yokoi, T Takui

SYNTHETIC METALS 137 ( 1-3 ) 1213 - 1214 2003.4

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

Oxidative direct coupling of metalloporphyrins

Y Nakamura, N Aratani, A Tsuda, A Osuka, K Furukawa, T Kato

JOURNAL OF PORPHYRINS AND PHTHALOCYANINES 7 ( 4-5 ) 264 - 269 2003

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

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.

Low-dimensional molecule-based magnets with hydrogen-bonded network

M Sakai, J Toyoda, M Mitsumi, K Nakasuji, K Furukawa, D Shiomi, K Sato, T Takui

SYNTHETIC METALS 121 ( 1-3 ) 1776 - 1777 2001.3

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

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

A Novel Spin Wave from Low-Dimensional Superlatticce of Microstructured Ferromagnetic Thin Films

K. Furukawa, D. Shiomi, K. Sato, T. Takui, K. Itoh, A. Maeda, M. Kume, K. Shibata, I. Nakatani

Mol. Cryst. Liq. Cryst. 335 163 - 172 1999

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