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

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