九州大学 研究者情報
論文一覧
清水 宗治(しみず そうじ) データ更新日:2022.05.02

准教授 /  工学研究院 応用化学部門


原著論文
1. Yuta Shiina, Yuto Kage, Ko Furukawa, Heng Wang, Hirofumi Yoshikawa, Hiroyuki Furuta, Nagao Kobayashi, Soji Shimizu, TTF-Annulated Silicon Phthalocyanine Oligomers and Their External-Stimuli-Responsive Orientational Ordering, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 10.1002/anie.202011025, 59, 50, 22721-22730, 2020.12, 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..
2. Shoma Hirokawa, Shigeki Mori, Nagao Kobayashi, Soji Shimizu, Phenolate-bridged A2B-type subporphyrin dimer, Journal of Porphyrins and Phthalocyanines, 10.1142/s1088424621500796, A-F, 2021.07, An ether cleavage reaction of A2B-type subporphyrin bearing an ortho-anisyl substituent afforded a phenolate-bridged dimer. A head-to-tail structure of the dimer was unambiguously elucidated by single crystal X-ray diffraction analysis. UV-vis absorption and magnetic circular dichroism spectra indicated a minor interaction between the subporphyrin chromophores. Density functional theory calculations provided a detailed insight into the electronic structures of the subporphyrin dimer..
3. Shoma Hirokawa, Nagao Kobayashi, Soji Shimizu, Periphery-Fused Chiral A2B-Type Subporphyrin, Molecules, 10.3390/molecules26041140, 26, 4, 1140-1140, 2021.02, Despite significant interest, the chiroptical properties of subporphyrins have rarely been investigated because chiral subporphyrins are elusive. Here, inherently chiral subporphyrins are elaborated by forming a fused pyran ring at the periphery of an A2B-type meso-aryl-substituted subporphyrin. Their circular dichroism (CD) properties are largely affected by the peripheral substituents and the dihedral angles between the meso-aryl substituents and the subporphyrin core: the β-perbromo subporphyrin with an orthogonal arrangement of the meso-phenyl substituents to the subporphyrin core exhibits weak CD signals corresponding to the Q bands, whereas the unsubstituted species with smaller dihedral angles shows relatively intense CD signals. A detailed structure–property relationship of these chiral subporphyrins was elucidated by time-dependent (TD) DFT calculations. This study reveals that the CD properties of chiral subporphyrins can be controlled by peripheral substitution and meso-aryl substituents..
4. Toshiharu Ishizaki, Hideaki Karasaki, Yuto Kage, Misaki Kamioka, Yitong Wang, Shigeki Mori, Naoto Ishikawa, Takamitsu Fukuda, Hiroyuki Furuta, Soji Shimizu, Janus Pyrrolopyrrole Aza‐dipyrrin: Hydrogen‐Bonded Assemblies and Slow Magnetic Relaxation of the Cobalt(II) Complex in the Solid State, Chemistry – A European Journal, 10.1002/chem.202101755, 27, 49, 12686-12692, 2021.09.
5. Yuto Kage, Seongsoo Kang, Shigeki Mori, Masashi Mamada, Chihaya Adachi, Dongho Kim, Hiroyuki Furuta, Soji Shimizu, An Electron‐Accepting aza‐BODIPY‐Based Donor–Acceptor–Donor Architecture for Bright NIR Emission, Chemistry – A European Journal, 10.1002/chem.202005360, 27, 16, 5259-5267, 2021.03.
6. Biju Basumatary, Ikuho Hashiguchi, Shigeki Mori, Soji Shimizu, Masatoshi Ishida, Hiroyuki Furuta, Copper 1,19-Diaza-21,24-dicarbacorrole: A Corrole Analogue with an N−N Linkage Stabilizes a Ground-State Singlet Organocopper Species, Angewandte Chemie - International Edition, 10.1002/anie.202005167, 59, 37, 15897-15901, 2020.09, © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A copper complex of a heterocorrole analogue with an N–N linkage, 1,19-diaza-21,24-dicarbadibenzocorrole (Cu-5), was successfully synthesized via oxidative metalation–cyclization of a tetrapyrrolic precursor. The N–N linkage in the skeleton of Cu-5, which serves as a mediator of π-electron delocalization, features an 18π aromatic system. The electronic structure of Cu-5 is best described as a ground-state singlet species stabilized by the distinct NNCC coordination core. This finding shows how the ligand's design can be used to modulate the Cu (Formula presented.) orbital energy, thereby making such compounds invaluable for copper-based catalytic applications..
7. Ru Feng, Narumi Sato, Mayuka Nomura, Akinori Saeki, Hajime Nakanotani, Chihaya Adachi, Takuma Yasuda, Hiroyuki Furuta, Soji Shimizu, Near-infrared absorbing pyrrolopyrrole aza-BODIPY-based donor-acceptor polymers with reasonable photoresponse, Journal of Materials Chemistry C, 10.1039/d0tc01487g, 8, 26, 8770-8776, 2020.07, © The Royal Society of Chemistry. Designing near-infrared (NIR) absorbing donor-acceptor (D-A) polymers with photoresponse beyond 900 nm has remained a challenge in the area of organic photovoltaics (OPV) owing to the limited kinds of strong electron acceptors. Here we present the use of pyrrolopyrrole aza-BODIPY (PPAB) as a new acceptor group in D-A polymers in place of a conventional diketopyrrolopyrrole acceptor to achieve power conversion efficiencies up to 2.27% despite the ultra-small bandgap of 1.08 eV. The small photon energy loss of the PPAB-based D-A polymer and moderately high short-circuit current of 8.52 mA cm-2 arising from the panchromatic visible/NIR absorption guarantee PPAB as a potential building block of D-A polymers for NIR photovoltaics. This journal is.
8. Soji Shimizu, 5,15-Diheteroporphyrins synthesized from α,α'dihalodipyrrin as a key building block, Heterocycles, 10.3987/REV-20-927, 100, 8, 1123-1162, 2020.04, © 2020 The Japan Institute of Heterocyclic Chemistry A facile synthesis of meso-aryl-substituted α,α'-dihalodipyrrins and their use as starting materials in the porphyrin synthesis have enabled creation of various porphyrin analogues containing heteroatoms at two opposite meso-positions, namely 5,15-positions. Incorporation of lone pair electrons into the 18π-electron aromatic conjugated system of porphyrin allows the system to attain antiaromaticity with unique optical and electrochemical properties. This review summarizes the recent development in the chemistry of 5,15-diheteroporphyrins synthesized from meso-aryl-substituted α,α'-dihalodipyrrins..
9. Ru Feng, Narumi Sato, Takuma Yasuda, Hiroyuki Furuta, Soji Shimizu, Rational design of pyrrolopyrrole-aza-BODIPY-based acceptor-donor-acceptor triads for organic photovoltaics application, Chemical Communications, 10.1039/d0cc00398k, 56, 20, 2975-2978, 2020.03, This journal is © The Royal Society of Chemistry. Acceptor-donor-acceptor triads consisting of diketopyrrolopyrrole (DPP) or pyrrolopyrrole aza-BODIPY (PPAB) or both as acceptors and cyclopentadithiophene as a donor were rationally designed for near infrared (NIR) photovoltaics application. Among them, the PPAB-based triad exhibited the highest power conversion efficiency of 3.88% owing to the panchromatic absorption in the UV/vis/NIR regions..
10. Takaaki Yamamoto, Jibin Alex Abraham, Shigeki Mori, Motoki Toganoh, Soji Shimizu, Masatoshi Ishida, Hiroyuki Furuta, Tungsten(VI) Complex of N-Fused Porphyrin Absorbing Near-Infrared Light beyond 1000 nm, Chemistry - An Asian Journal, 10.1002/asia.202000014, 15, 6, 748-752, 2020.03, © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Incorporating tungsten into the N3 core of a N-fused porphyrin (NFP; 1) affords high-valent tungsten(VI)-NFP complexes, WClO2-1 and 21-chlorinated WClO2-3. The X-ray structure of WClO2-1 reveals a distorted octahedral geometry with sitting atop metal coordination. The absorption spectrum of WClO2-1 displays bathochromically shifted Q-like bands beyond 1000 nm, indicating an inherently narrow HOMO-LUMO energy gap. DFT calculations show that the degeneracy of the LUMO and LUMO+1 pair of 1 is significantly resolved by the tungsten(VI) coordination. Conclusively, magnetic circular dichroism (MCD) spectroscopy and cyclic voltammetry provide a rationale for the narrow HOMO-LUMO energy gap in the “16-electron” d0 tungsten(VI)-NFP complexes..
11. Yuto Kage, Soji Shimizu, Gabriele Kociok-Köhn, Hiroyuki Furuta, G. Dan Pantoş, Subphthalocyanine-Stoppered [2]Rotaxanes: Synthesis and Size/Energy Threshold of Slippage, Organic Letters, 10.1021/acs.orglett.9b04620, 22, 3, 1096-1101, 2020.02, © 2020 American Chemical Society. Subphthalocyanine (SubPc)-stoppered [2]rotaxanes were synthesized for the first time. The rotaxane bearing unsubstituted SubPc as a stopper exhibited an equilibrium of slipping-on and slipping-off, whereas a perfluorinated SubPc stopper completely blocked slippage of the ring due to its slightly larger size. Kinetic studies revealed the Gibbs free energy of activation for the slipping-on and slipping-off processes. The optical properties of the rotaxanes, including photoinduced electron transfer, were also revealed..
12. Akihide Nishiyama, Yuki Tanaka, Shigeki Mori, Hiroyuki Furuta, Soji Shimizu, Oxidative nitration reaction of antiaromatic 5,15-dioxaporphyrin, Journal of Porphyrins and Phthalocyanines, 10.1142/S108842461950113X, 24, 1-3, 355-361, 2020.01, © 2020 World Scientific Publishing Company. Upon oxidation of 20π-electron antiaromatic 5,15-dioxaporphyrin (DOP) using nitrosonium ions as oxidants, a tetrakis-β-nitrated compound was formed instead of the expected 18π-electron aromatic dication species via an oxidative nitration reaction mechanism. Compared with the original DOP, this tetranitro DOP product exhibited a blue shift of absorption and downfield shifts of the β-pyrrolic proton signals. The unique antiaromatic electronic structure of the tetranitro DOP was disclosed experimentally by electrochemistry and theoretically by DFT and NICS calculations..
13. Ryo Nozawa, Jinseok Kim, Juwon Oh, Anna Lamping, Yemei Wang, Soji Shimizu, Ichiro Hisaki, Tim Kowalczyk, Heike Fliegl, Dongho Kim, Hiroshi Shinokubo, Three-dimensional aromaticity in an antiaromatic cyclophane, Nature Communications, 10.1038/s41467-019-11467-4, 10, 1, 2019.12, © 2019, The Author(s). Understanding of interactions among molecules is essential to elucidate the binding of pharmaceuticals on receptors, the mechanism of protein folding and self-assembling of organic molecules. While interactions between two aromatic molecules have been examined extensively, little is known about the interactions between two antiaromatic molecules. Theoretical investigations have predicted that antiaromatic molecules should be stabilized when they stack with each other by attractive intermolecular interactions. Here, we report the synthesis of a cyclophane, in which two antiaromatic porphyrin moieties adopt a stacked face-to-face geometry with a distance shorter than the sum of the van der Waals radii of the atoms involved. The aromaticity in this cyclophane has been examined experimentally and theoretically. This cyclophane exhibits three-dimensional spatial current channels between the two subunits, which corroborates the existence of attractive interactions between two antiaromatic π-systems..
14. Yuto Kage, Hideaki Karasaki, Shigeki Mori, Hiroyuki Furuta, Soji Shimizu, Pyrrolopyrrole Aza-BODIPY Analogues as Near-Infrared Chromophores and Fluorophores: Red-Shift Effects of Substituents on Absorption and Emission Spectra, ChemPlusChem, 10.1002/cplu.201900226, 84, 11, 1648-1652, 2019.11, © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Pyrrolopyrrole aza-BODIPY analogues (PPABs) are a new class of UV/vis and near-infrared chromophores. Varying the substituents results in red-shifts of both the absorption and emission spectra. Extension of the lengths of the oligothiophene substituents from thiophene to quaterthiophene caused red-shifts of the absorption and emission from 699 and 712 nm to 809 and 853 nm, respectively. The piperidylthiophene-substituted PPAB exhibited similar red-shifts of the absorption and emission to 810 and 831 nm, respectively, although only a single thienyl component is present, because of the strong electron-donating nature of the piperidine substituent..
15. Yemei Wang, Shigeki Mori, Hiroyuki Furuta, Soji Shimizu, Bis(1,3-dithiol-2-ylidene)-Substituted Subtriazachlorin: A Subphthalocyanine Analogue with Redox Properties, Angewandte Chemie - International Edition, 10.1002/anie.201905331, 58, 32, 10975-10979, 2019.08, © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Bis(1,3-dithiol-2-ylidene)-substituted subtriazachlorin was formed because of an unusual reaction of a 1,3-dithiole-2-one-fused subphthalocyanine in a triethylphosphite-mediated tetrathiafulvalene synthesis. In this novel molecule, the bis(1,3-dithiol-2-ylidene)ethane moiety and subtriazachlorin structure are fused, resulting in an electron-donating ability and broad absorption in the near-infrared region..
16. Ryoichi Ishimatsu, Hirosato Shintaku, Yuto Kage, Misaki Kamioka, Soji Shimizu, Koji Nakano, Hiroyuki Furuta, Toshihiko Imato, Efficient Electrogenerated Chemiluminescence of Pyrrolopyrrole Aza-BODIPYs in the Near-Infrared Region with Tripropylamine: Involving Formation of S2 and T2 States, Journal of the American Chemical Society, 10.1021/jacs.9b05245, 141, 30, 11791-11795, 2019.07, © 2019 American Chemical Society. Efficient electrogenerated chemiluminescences (ECLs) of three pyrrolopyrrole aza-BODIPYs in the near-infrared region by using tripropylamine as a coreactant are reported. Kinetic analysis based on Marcus theory indicates the direct formation of S2 and T2 states through the electron transfer reaction, which affects the ECL efficiencies..
17. Soji Shimizu, Aza-BODIPY synthesis towards vis/NIR functional chromophores based on a Schiff base forming reaction protocol using lactams and heteroaromatic amines, Chemical Communications, 10.1039/c9cc03365c, 55, 60, 8722-8743, 2019.06, © 2019 The Royal Society of Chemistry. Aza-BODIPY is a class of heteroatom-containing BODIPY analogues targeting near infrared (NIR) chromophores and fluorophores. As a synthetic strategy towards aza-BODIPY structures, we have, recently, developed a Schiff base forming reaction using readily available lactams and heteroaromatic amines. Absorption and fluorescence of a series of compounds cover the whole range of the ultraviolet (UV)/visible (vis)/NIR regions. In addition, some compounds exhibit solid state emission, aggregation-induced emission enhancement, tunable fluorescence in the vis/NIR regions and non-linear optical properties. Furthermore, simple dimerization of aza-BODIPY chromophores caused unusual panchromatic absorption, whereas in combination with an N-confused porphyrin skeleton, multi-state NH tautomerism was achieved. In this Feature Article, wide applicability of this Schiff base forming reaction and optical and electrochemical properties of aza-BODIPY analogues thus synthesized are summarized including recent applications, such as bioimaging, photothermal cancer therapy and organic photovoltaics..
18. Yemei Wang, Koya Uchihara, Shigeki Mori, Hiroyuki Furuta, Soji Shimizu, 1,3-Dithiole-2-one-Fused Subphthalocyanine and Subporphyrazine: Synthesis and Properties Arising from the 1,3-Dithiole-2-one Units, Organic Letters, 10.1021/acs.orglett.9b00752, 21, 9, 3103-3107, 2019.05, © 2019 American Chemical Society. Subphthalocyanine (SubPc) and its benzo ring-removed analogue, subporphyrazine (SubPz), bearing 1,3-dithiole-2-one (S 2 CO) groups as a new class of substituents were synthesized. In addition to the perturbed optical properties due to the presence of electron-withdrawing S 2 CO units, the deep bowl-shaped structure of the SubPz derivative allowed concave-convex interaction to form a unique co-crystal structure with C 60 . Finally, using the reactivity of the peripheral S 2 CO units, S 2 CO-fused SubPc was successfully converted into tetrathiafulvalene (TTF)-annulated SubPc in a yield higher than that of the direct synthesis from a TTF-fused phthalonitrile..
19. Masaya Fukuda, Shigeki Mori, Hiroyuki Furuta, Soji Shimizu, N-Confused Porphyrin-aza-Dipyrrin Chimera: A Versatile Metal Coordination Ligand Using its Unique NH Tautomerism, Chemistry - An Asian Journal, 10.1002/asia.201801750, 14, 10, 1697-1702, 2019.05, © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A novel N-confused porphyrin (NCP) analogue bearing an external aza-dipyrrin-like coordination site was synthesized by a Schiff-base forming reaction of N-confused oxoporphyrin and 2-aminopyridine derivatives. The chimera molecule enhances the intrinsic NH tautomerism of NCP to enable four possible tautomeric structures, three of which were identified by metal coordination..
20. Keisuke Sudoh, Ko Furukawa, Haruyuki Nakano, Soji Shimizu, Yoshihiro Matano, Synthesis and properties of redox-switchable zinc complexes of 10,15,20-triaryl-15-aza-5-oxaporphyrin, Heteroatom Chemistry, 10.1002/hc.21456, 29, 5-6, 2018.12, © 2018 Wiley Periodicals, Inc. 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 20π TriAAOP in the neutral form. Oxidation of 20π TriAAOP with silver (I) hexafluorophosphate generated the 19π radical cation or 18π dication depending on the content of oxidant used. The interconversion between the three oxidation states (18π, 19π, and 20π) resulted in distinct changes in the aromaticity and optical properties of the 15-aza-5-oxaporphyrin π-system. Nuclear magnetic resonance spectroscopy of 20π TriAAOP revealed its antiaromatic character, whereas that of the 18π 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 19π and 18π 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 π-systems were energetically stabilized relative to those of the TADAP π-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..
21. Akihide Nishiyama, Masaya Fukuda, Shigeki Mori, Ko Furukawa, Heike Fliegl, Hiroyuki Furuta, Soji Shimizu, Rational Synthesis of Antiaromatic 5,15-Dioxaporphyrin and Oxidation into β,β-Linked Dimers, Angewandte Chemie - International Edition, 10.1002/anie.201804648, 57, 31, 9728-9733, 2018.07, © 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..
22. Kento Ueta, Masaya Fukuda, Gakhyun Kim, Soji Shimizu, Takayuki Tanaka, Dongho Kim, Atsuhiro Osuka, The First Silicon(IV) Corrole Complexes: Synthesis, Structures, Properties, and Formation of a μ-Oxo Dimer, Chemistry - A European Journal, 10.1002/chem.201800165, 24, 30, 7637-7646, 2018.05, © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The first SiIV corrole complexes were synthesized in good yields by treatment of meso-triarylcorroles with tetrachlorosilane in 1,2-dichloroethane at 60 °C. The central silicon atom possesses a square-pyramidal coordination geometry with slightly longer Si−N bond lengths as compared with those of known triazacorrole SiIV complexes. The SiIV corrole complexes exhibit sharp and blue-shifted absorption spectra and larger fluorescence quantum yields as compared with the corresponding free-base corroles. A μ-oxo dimer of a SiIV corrole was synthesized upon treatment with methanesulfonyl chloride in pyridine at 100 °C. This dimer shows a face-to-face structure with a 90° twist in the solid state. Although the dimer exhibits a blue-shifted Soret band, reflecting the face-to-face geometry, it displays a largely red-shifted and broad fluorescence spectrum with a large Stokes shift, suggesting a large structural change in the S1 state. These intriguing optical properties have been comprehensively studied by magnetic circular dichroism (MCD) spectroscopy, femtosecond transient absorption (fs-TA) measurements, and theoretical calculations..
23. Yuto Kage, Shigeki Mori, Marina Ide, Akinori Saeki, Hiroyuki Furuta, Soji Shimizu, Blackening of aza-BODIPY analogues by simple dimerization: panchromatic absorption of a pyrrolopyrrole aza-BODIPY dimer, Materials Chemistry Frontiers, 10.1039/c7qm00438a, 2, 1, 112-120, 2017.11,

Dimerization of the so-called pyrrolopyrrole aza-BODIPY via a bithienyl linkage led to the creation of a novel black dye with dual emission and panchromatic absorption properties in the Vis/NIR region.

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24. Fumiya Iizuka, Yuto Kage, Nagao Kobayashi, Hiroyuki Furuta, Soji Shimizu, Phenylene-Bridged Expanded Porphyrazines, ChemPlusChem, 10.1002/cplu.201600482, 82, 7, 1021-1024, 2017.08, © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Novel expanded porphyrazines comprising o- and p-phenylene units were synthesized from self-condensation reactions of acyclic [2+1]-type precursors prepared from 1,3-diiminoisoindoline and the corresponding phenylenediamines. Möbius and Hückel topological structures of [4+2]-type and [3+2]-type expanded porphyrazines, respectively, were elucidated by X-ray crystallography. Despite the Möbius and Hückel [4n]π-electron systems, these expanded porphyrazines are virtually nonaromatic as a result of their flexible structures in solution, which may diminish intrinsic aromaticity and antiaromaticity..
25. Masamichi Tamada, Taku Iino, Yemei Wang, Marina Ide, Akinori Saeki, Hiroyuki Furuta, Nagao Kobayashi, Soji Shimizu, Facile synthesis of dimeric aza-BODIPY analogues from electron-deficient bislactams and their intriguing optical and electrochemical properties, Tetrahedron Letters, 10.1016/j.tetlet.2017.06.088, 58, 32, 3151-3154, 2017.06, © 2017 Elsevier Ltd Electron-deficient bislactams, isoindigo and benzodipyrrolidone, were converted into dimeric aza-BODIPY analogues by a Schiff base forming reaction. These novel aza-BODIPY analogues exhibited bathochromically-shifted absorption and anodic shifts of the reduction potentials, implying their potential application as n-type chromophores in optoelectronics..
26. Soji Shimizu, Creation of novel functional molecules based on structural modification of phthalocyanine, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.75.1012, 75, 10, 1012-1022, 2017.05, Phthalocyanine is a fascinating conjugated molecule owing to the unique optical and electrochemical properties arising from the 18π -electron conjugated system, and it has been utilized in a variety of fields related to our daily life. Creation of novel functional molecules based on the structural modification of this molecule have, therefore, been of great importance. In the last decade, we have developed the synthesis of phthalocyanine analogues by core-modification as well as peripheral modification and revealed their unique optical and electrochemical properties. In addition, based on the knowledge obtained during the phthalocyanine research, we have developed a novel Schiff-base forming reaction, which provided a variety of aza-BODIPY analogues with unique absorption and emission in the visible and near infrared region. Application studies using these functional molecules as an organic photovoltaic material have also been conducted. In this account, the synthesis and structure-property relationship of these novel phtha- locyanine-based functional molecules are described..
27. Soji Shimizu, Recent Advances in Subporphyrins and Triphyrin Analogues: Contracted Porphyrins Comprising Three Pyrrole Rings, Chemical Reviews, 10.1021/acs.chemrev.6b00403, 117, 4, 2730-2784, 2017.02, © 2016 American Chemical Society. Subporphyrinato boron (subporphyrin) was elusive until the syntheses of tribenzosubporphine in 2006 and meso-aryl-substituted subporphyrin in 2007. These novel contracted analogues possess a 14 electron conjugated system embedded in a bowl-shaped structure. They exhibit absorption and fluorescence in the UV/vis region and nonlinear optical properties due to their octupolar structures. The unique coordination geometry around the central boron atom in the structure of subporphyrin enabled investigation of rare boron species, such as borenium cations, boron hydrides, and boron peroxides. Along with the burgeoning development of the chemistry of subporphyrins, analogous triphyrin systems have also emerged. Their rich coordination chemistry as a result of their free-base structures, which are different from the boron-coordinating structure of subporphyrins, has been intensively investigated. On the basis of the unique structures and reactivities of subporphyrins and their related triphyrin analogues, supramolecular architectures and covalently linked multicomponent systems have also been actively pursued. This Review provides an overview of the development of subporphyrin and triphyrin chemistry in the past decade and future prospects in this field, which may inspire molecular design toward applications based on their unique properties..
28. Koji Miki, Akane Enomoto, Tatsuhiro Inoue, Tatsuya Nabeshima, Sousuke Saino, Soji Shimizu, Hideki Matsuoka, Kouichi Ohe, Polymeric Self-Assemblies with Boron-Containing Near-Infrared Dye Dimers for Photoacoustic Imaging Probes, Biomacromolecules, 10.1021/acs.biomac.6b01568, 18, 1, 249-256, 2017.01, © 2016 American Chemical Society. Polymers containing pyrrolopyrrole aza-BODIPY (PPAB) and thiophene-bridged BODIPY dimers (TBD) having poly(ethylene glycol) (PEG) or PEGylated hyaluronic acid (HA) were prepared by facile conjugation approaches. Self-assemblies consisting of TBD-conjugated polymers more efficiently generated photoacoustic (PA) signals than PPAB-PEG conjugate upon irradiation with near-infrared pulsed laser light. Among dye-conjugated polymers examined, TBD-HA-PEG conjugates efficiently generated photoacoustic signals, 1.49-1.83 times stronger than that of commercially available indocyanine green (ICG). We found that the following two factors are essential to enhance PA signals from self-assemblies: (1) the formation of strongly interacting TBD aggregates and (2) enhancement of the elastic modulus of self-assemblies by conjugating TBDs with HA. TBD-conjugated HA derivatives circulated in blood vessels for a longer time (15.6 ± 4.9% injected dose (ID) in blood 24 h after injection) and more specifically accumulated in tumor tissues (17.8 ± 3.5% ID/g in tumor 24 h after injection) than ICG-conjugated HA derivatives, visualizing a tumor site more clearly. The cell uptake experiment of dye-HA conjugates indicates that ICG-conjugated polymers internalized into cells or merged with cell walls to emit strong fluorescence, while TBD-conjugated polymers were not internalized into cells. Because the disassembly of the TBD-conjugated HA derivatives is suppressed, aggregated TBDs emit weak fluorescence but efficiently generate strong PA signals in tumor tissues..
29. Masatoshi Ishida, Hiroyuki Fujimoto, Tatsuki Morimoto, Shigeki Mori, Motoki Toganoh, Soji Shimizu, Hiroyuki Furuta, Supramolecular dimeric structures of pyrazole-containing meso-oxo carbaphlorin analogues, Supramolecular Chemistry, 10.1080/10610278.2016.1158408, 29, 1, 8-16, 2017.01, © 2016 Informa UK Limited, trading as Taylor & Francis Group. Synthesis and properties of a novel meso-oxo carbaphlorin analogue embedded with an N-free pyrazole moiety are described. The N-benzyl precursor was prepared by a [3 + 1]-MacDonald condensation of N-benzyl pyrazole dialdehyde and β-alkyl-substituted tripyrrane dicarboxylic acid and subsequent oxidation by ferric chloride. Upon deprotection of the benzyl group, the resulting N-free oxophlorin analogue formed a unique supramolecular dimer through mutual hydrogen bonding interactions between the pyrazole NH and meso-carbonyl group. The assembled behaviour was characterised by various spectroscopies, X-ray crystallographic analysis and vapour pressure osmometry. Under the similar reaction conditions, the condensation of meso-phenyl-substituted tripyrrane derivative afforded an unprecedented tetrapyrrolic macrocycle fused with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone unit at their α-pyrrolic positions. The X-ray crystallographic analysis of the macrocycle revealed a twisted core structure, and nonaromatic nature was elucidated..
30. Ryo Nozawa, Hiroko Tanaka, Won Young Cha, Yongseok Hong, Ichiro Hisaki, Soji Shimizu, Ji Young Shin, Tim Kowalczyk, Stephan Irle, Dongho Kim, Hiroshi Shinokubo, Stacked antiaromatic porphyrins, Nature Communications, 10.1038/ncomms13620, 7, 2016.11, © The Author(s) 2016. Aromaticity is a key concept in organic chemistry. Even though this concept has already been theoretically extrapolated to three dimensions, it usually still remains restricted to planar molecules in organic chemistry textbooks. Stacking of antiaromatic π-systems has been proposed to induce three-dimensional aromaticity as a result of strong frontier orbital interactions. However, experimental evidence to support this prediction still remains elusive so far. Here we report that close stacking of antiaromatic porphyrins diminishes their inherent antiaromaticity in the solid state as well as in solution. The antiaromatic stacking furthermore allows a delocalization of the π-electrons, which enhances the two-photon absorption cross-section values of the antiaromatic porphyrins. This feature enables the dynamic switching of the non-linear optical properties by controlling the arrangement of antiaromatic π-systems on the basis of intermolecular orbital interactions..
31. Yuta Shiina, Hideaki Karasaki, Shigeki Mori, Nagao Kobayashi, Hiroyuki Furuta, Soji Shimizu, A novel isoindole-containing polyaromatic hydrocarbon unexpectedly formed during the synthesis of meso-2,6-dichlorophenyl-substituted tribenzosubporphyrin, Journal of Porphyrins and Phthalocyanines, 10.1142/S1088424616500541, 20, 8-11, 1049-1054, 2016.08, © 2016 World Scientific Publishing Company. A novel isoindole-containing polyaromatic hydrocarbon was unexpectedly formed during the synthesis of meso-2,6-dichlorophenyl-substituted tribenzosubporphyrin from a reaction of phthalimide and 2,6-dichlorophenylacetic acid in the presence of boric acid. Due to the highly annulated structure, this molecule exhibited blue color in solution, which was theoretically well reproduced by the HOMO-LUMO transitions based on the time-dependent DFT calculation. In this manuscript, the synthesis and properties of this polyaromatic hydrocarbon and meso-2,6-dichlorophenyl-substituted tribenzosubporphyrin are reported..
32. Shota Nakano, Yuto Kage, Hiroyuki Furuta, Nagao Kobayashi, Soji Shimizu, Pyrene-Bridged Boron Subphthalocyanine Dimers: Combination of Planar and Bowl-Shaped π-Conjugated Systems for Creating Uniquely Curved π-Conjugated Systems, Chemistry - A European Journal, 10.1002/chem.201600548, 22, 23, 7706-7710, 2016.06, © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Pyrene-bridged boron subphthalocyanine dimers were synthesized from a mixed-condensation reaction of 2,7-di-tert-butyl-4,5,9,10-tetracyanopyrene and tetrafluorophthalonitrile, and their syn and anti isomers arising from the result of connecting two bowl-shaped boron subphthalocyanine molecules were successfully separated. Expansion of the conjugated system of boron subphthalocyanine through a pyrene bridge caused a redshift of the Q band absorption relative to the parent pyrene-fused monomer, whereas combining the curved π-conjugation of boron subphthalocyanine with the planar π-conjugation of pyrene enabled facile embracement of C60 molecules, owing to the enhanced concave-convex π-π stacking interactions. Pyrene-bridged boron subphthalocyanine (SubPc) dimers were synthesized from a mixed-condensation reaction of tetracyanopyrene and tetrafluorophthalonitrile, and their syn and anti isomers were successfully separated. In addition to the redshift of the Q band absorption, combining the curved π-conjugation of SubPc with the planar π-conjugation of pyrene enabled facile embracement of C60 molecules, owing to the enhanced concave-convex π-π stacking interactions..
33. Soji Shimizu, Hiroyuki Furuta, Core-modified phthalocyanines and subphthalocyanines: A synthetic strategy towards core-modification and novel properties arising from the inner ring-expansion, Macroheterocycles, 10.6060/mhc151102s, 8, 4, 332-342, 2015.12, © ISUCT Publishing. This microreview covers contribution of the authors in the synthesis of novel “core-modified phthalocyanines and subphthalocyanines” bearing a larger ring unit than a five-membered pyrrole ring in the core. The core-modification does not only cause structural deformation, but also causes significant changes in the optical and electrochemical properties..
34. Soji Shimizu, Ai Murayama, Takuya Haruyama, Taku Iino, Shigeki Mori, Hiroyuki Furuta, Nagao Kobayashi, Benzo[c,d]indole-Containing Aza-BODIPY Dyes: Asymmetrization-Induced Solid-State Emission and Aggregation-Induced Emission Enhancement as New Properties of a Well-Known Chromophore, Chemistry - A European Journal, 10.1002/chem.201501464, 21, 37, 12996-13003, 2015.09, © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A series of symmetric and asymmetric benzo[c,d]indole-containing aza boron dipyrromethene (aza-BODIPY) compounds was synthesized by a titanium tetrachloride-mediated Schiff-base formation reaction of commercially available benzo[c,d]indole-2(1H)-one and heteroaromatic amines. These aza-BODIPY analogues show different electronic structures from those of regular aza-BODIPYs, with hypsochromic shifts of the main absorption compared to their BODIPY counterparts. In addition to the intense fluorescence in solution, asymmetric compounds exhibited solid-state fluorescence due to significant contribution of the vibronic bands to both absorption and fluorescence as well as reduced fluorescence quenching in the aggregates. Finally, aggregation-induced emission enhancement, which is rare in BODIPY chromophores, was achieved by introducing a nonconjugated moiety into the core structure..
35. Fengkun Chen, Yong Seok Hong, Soji Shimizu, Dongho Kim, Takayuki Tanaka, Atsuhiro Osuka, Synthesis of a Tetrabenzotetraaza[8]circulene by a "fold-In" Oxidative Fusion Reaction, Angewandte Chemie - International Edition, 10.1002/anie.201505124, 54, 36, 10639-10642, 2015.09, © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Tetrabenzotetraaza[8]circulene (1) has been synthesized in good yield by a "fold-in" oxidative fusion reaction of a 1,2-phenylene-bridged cyclic tetrapyrrole. X-ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic-like character, such as sharp absorption bands, high fluorescence quantum yields (ΦF=0.55 in THF), and a single exponential fluorescence decay with τF=3.8 ns. These observations indicate a dominant contribution of an [8]radialene-like π conjugation and hence aromatic character of the local aromatic segments in 1..
36. Yuta Saegusa, Tomoya Ishizuka, Keiyu Komamura, Soji Shimizu, Hiroaki Kotani, Nagao Kobayashi, Takahiko Kojima, Ring-fused porphyrins: Extension of π-conjugation significantly affects the aromaticity and optical properties of the porphyrin π-systems and the Lewis acidity of the central metal ions, Physical Chemistry Chemical Physics, 10.1039/c5cp01420d, 17, 22, 15001-15011, 2015.06, © the Owner Societies 2015. Here, we report the effects of ring fusion, which causes expansion of the π-conjugation circuits of the porphyrin derivatives to the fused meso-aryl groups, on the aromaticity and the magnetic properties of porphyrin derivatives. These studies revealed the facts that the ring fusion with five-membered rings causes not only the remarkable red shifts of the absorption bands and narrowed HOMO-LUMO gaps, but also the contribution of anti-aromatic resonance forms to the magnetic properties as observed in the 1H NMR spectra. The optical absorption and magnetic circular dichroism (MCD) spectroscopies indicate that the increase in the number of the fused rings causes stabilization of the LUMO level of the porphyrin derivatives and as a result induces the loosening of the LUMO degeneracy that is generally observed for porphyrins. The electronic structure of a quadruply fused porphyrin derivative was experimentally clarified by the ESR studies on the 1e--oxidized and 1e--reduced species in THF. Furthermore, we revealed the substituent effects of the fused meso-aryl groups of quadruply fused porphyrins (QFPs) on the crystal structures, absorption spectra and redox potentials; the sensitiveness of the substituent effects shows that the π-conjugation circuits extended to the fused meso-aryl groups. Additionally, the elongation of the bond lengths between the pyrrolic nitrogen and the central metal ions in QFP-metal complexes causes a remarkable increase of the Lewis acidity of the central metal ions..
37. Quan Liu, Soji Shimizu, Nagao Kobayashi, Cyclophanes Containing Bowl-Shaped Aromatic Chromophores: Three Isomers of anti-[2.2](1,4)Subphthalocyaninophane, Angewandte Chemie - International Edition, 10.1002/anie.201411510, 54, 17, 5187-5191, 2015.04, © 2015 Wiley-VCH Verlag GmbH & Co. KGaA. The connection of bowl-shaped aromatic boron subphthalocyanines with anti-[2.2]paracyclophane resulted in the first observation of electronic communication between convex and concave surfaces. Three isomers of anti-[2.2](1,4)subphthalocyaninophane, described as concave - concave (CC), convex - concave (CV), and convex - convex (VV) according to the orientation of the subphthalocyanine units, were synthesized and characterized by various spectroscopic techniques, including 1H NMR, electronic absorption, fluorescence, and magnetic circular dichroism spectroscopy and X-ray crystallography, together with molecular-orbital calculations. On going from the CC system to CV and further to VV, the Q band broadened and finally split as a result of through-space expansion of the conjugated systems, which were also reproduced theoretically..
38. Soji Shimizu, Taku Iino, Akinori Saeki, Shu Seki, Nagao Kobayashi, Rational molecular design towards Vis/NIR absorption and fluorescence by using pyrrolopyrrole aza-BODIPY and its highly conjugated structures for organic photovoltaics, Chemistry - A European Journal, 10.1002/chem.201405761, 21, 7, 2893-2904, 2015.02, © 2015 Wiley-VCH Verlag GmbH & Co. KGaA. Pyrrolopyrrole aza-BODIPY (PPAB) developed in our recent study from diketopyrrolopyrrole by titanium tetrachloride-mediated Schiff-base formation reaction with heteroaromatic amines is a highly potential chromophore due to its intense absorption and fluorescence in the visible region and high fluorescence quantum yield, which is greater than 0.8. To control the absorption and fluorescence of PPAB, particularly in the near-infrared (NIR) region, further molecular design was performed using DFT calculations. This results in the postulation that the HOMO-LUMO gap of PPAB is perturbed by the heteroaromatic moieties and the aryl-substituents. Based on this molecular design, a series of new PPAB molecules was synthesized, in which the largest redshifts of the absorption and fluorescence maxima up to 803 and 850 nm, respectively, were achieved for a PPAB consisting of benzothiazole rings and terthienyl substituents. In contrast to the sharp absorption of PPAB, a PPAB dimer, which was prepared by a cross-coupling reaction of PPAB monomers, exhibited panchromatic absorption across the UV/Vis/NIR regions. With this series of PPAB chromophores in hand, a potential application of PPAB as an optoelectronic material was investigated. After identifying a suitable PPAB molecule for application in organic photovoltaic cells based on evaluation using time-resolved microwave conductivity measurements, a maximized power conversion efficiency of 1.27% was achieved..
39. Hui Liu, Hua Lu, Zhikuan Zhou, Soji Shimizu, Zhifang Li, Nagao Kobayashi, Zhen Shen, Asymmetric core-expanded aza-BODIPY analogues: Facile synthesis and optical properties, Chemical Communications, 10.1039/c4cc06704e, 51, 9, 1713-1716, 2015.01, © The Royal Society of Chemistry 2015. Significantly large Stokes shifts and enhanced solid state emissions were achieved in a novel series of asymmetric core-expanded aza-BODIPY analogues, 4a-4d, synthesized by a facile and scalable two-step reaction in high yields..
40. Soji Shimizu, Nagao Kobayashi, Recent Advances in the Chemistry of Phthalocyanines as Functional Chromophores, Chemical Science of Electron Systems, 10.1007/978-4-431-55357-1_16, 273-291, 2015.01, © Springer International Publishing Switzerland 2015. Phthalocyanine (Pc), a conventional dyestuff exhibiting vivid blue or green color, has been utilized as a functional molecule for application in a variety of fields due to its excellent optical and electrochemical properties. Creation of novel π-conjugated systems based on the structure of Pc with the aim of further developing unique properties has, therefore, been of a prime importance. Despite the over a hundred-year history of phthalocyanine chemistry, progress in this regard has been fairly limited mainly due to the problems inherent in the synthesis of Pc. The authors have pioneered this research area by focusing on the control of the optical properties in the visible and near-infrared regions by (1) creation of the novel π-conjugated systems and (2) introduction of perturbation that is as simple as possible to the electronic structures and have reported a variety of unprecedented Pc analogues. Considerable attention has also been focused on the structure-optical property relationships of these novel Pc compounds. This chapter summarizes the contribution of the authors to the recent advances in the chemistry of phthalocyanine as functional chromophore systems..
41. Xu Liang, Soji Shimizu, Nagao Kobayashi, Sizeable red-shift of absorption and fluorescence of subporphyrazine induced by peripheral push and pull substitution, Chemical Communications, 10.1039/c4cc05943c, 50, 89, 13781-13784, 2014.10, Peripheral substitution with electron-donating (push) and electron-withdrawing (pull) substituents caused a sizeable red-shift of the Q band absorption and fluorescence of subporphyrazine, and the red-shift was controlled by the push substituents. Control of the chromophore symmetry and inherent molecular chirality arising from the pattern of substitution were also investigated. © 2014 Partner Organisations..
42. Soji Shimizu, Shoma Hirokawa, Nagao Kobayashi, Unexpected formation of a triphyrin in the reaction of dibromodipyrromethene and N,N-dimethylaminoethanol, Journal of Porphyrins and Phthalocyanines, 10.1142/S1088424614500527, 18, 721-726, 2014.08, Copyright © 2014 World Scientific Publishing Company. A novel triphyrin was unexpectedly formed as a major by-product in the synthesis of mesoaryl-substituted dibenzo-5,10,15-triazaporphyrin from meso-aryl-substituted 1,9-dibromodipyrromethene and 5,6-diaryl-substituted 1,3-diiminoisoindoline in the presence of N,N-dimethylaminoethanol (DMAE). X-ray single crystal diffraction analysis elucidated that the terminal α-positions of this triphyrin were bridged by an N-methylaminoethoxy chain, which plausibly originated from DMAE during the reaction. The same compound was also obtained as a major product in the reaction of DMAE and meso-arylsubstituted 1,9-dibromodipyrromethene. Its unique properties, such as conformational fexibility of the bridging moiety and broad absorption in the visible region, were also revealed by1H NMR and UV-vis absorption spectroscopies..
43. Zhikuan Zhou, Yi Chang, Soji Shimizu, John Mack, Christian Schütt, Rainer Herges, Zhen Shen, Nagao Kobayashi, Core-modified rubyrins containing dithienylethene moieties, Angewandte Chemie - International Edition, 10.1002/anie.201402711, 53, 25, 6563-6567, 2014.06, Two stable core-modified rubyrins bearing one and two dithienylethene (DTE) units (1 and 2) have been synthesized. With one "closed-form" DTE unit, 1 shows aromaticity associated with its conjugated circuit of 26 π-electrons. In contrast, rubyrin 2 containing one "open-form" DTE unit has nonaromatic properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim..
44. Aiko Fukazawa, Hiroya Oshima, Soji Shimizu, Nagao Kobayashi, Shigehiro Yamaguchi, Dearomatization-Induced Transannular Cyclization: Synthesis of Electron-Accepting Thiophene-S,S-Dioxide-Fused Biphenylene, Journal of the American Chemical Society, 10.1021/ja503499n, 136, 24, 8738-8745, 2014.06, The transannular cyclization of dehydroannulenes bearing several alkyne moieties in close proximity is a powerful synthetic method for producing polycyclic aromatic hydrocarbons. We report that the reactivity can be switched by the aromaticity of the ring skeletons fused with the dehydroannulene core. Thus, while thiophene-fused bisdehydro[12]annulene 1 was handled as a stable compound in the air at room temperature, the oxidation with m-chloroperbenzoic acid from the aromatic thiophene rings to the nonaromatic thiophene-S,S-dioxides induced the transannular cyclization, even at room temperature, which was completed within 1 day to produce the formal [2 + 2] cycloadduct 3. This is in stark contrast to the fact that the thermal cyclization of 1 itself required heating at 80 °C for 9 days for completion. Experimental and theoretical studies indicate that the oxidation of even one thiophene ring in 1 sufficiently decreases the activation barrier for the transannular cyclization that proceeds through the 8π and 4π electrocyclic reaction sequence. The thiophene-S,S-dioxide-fused biphenylene 3 thus produced exhibits a set of intriguing properties, such as a higher electron affinity (E1/2 = -1.17 V vs Fc and Fc+) and a stronger fluorescence (φF = 0.20) than the other relevant biphenylene derivatives, which have electron-donating and nonfluorescent characteristics. © 2014 American Chemical Society..
45. Soji Shimizu, Nagao Kobayashi, Structurally-modified subphthalocyanines: Molecular design towards realization of expected properties from the electronic structure and structural features of subphthalocyanine, Chemical Communications, 10.1039/c4cc01526f, 50, 53, 6949-6966, 2014.06, This feature article summarizes recent contributions of the authors in the synthesis of structurally-modified subphthalocyanines. The structural modification covers (1) modification of the conjugated system of subphthalocyanines to create novel conjugated systems comprising three pyrroles or pyrrole-like subunits, (2) core-modification by expansion of the inner pyrrolic five-membered ring to larger six- and seven-membered ring units, and (3) exterior-modification by annulation of functional units to subphthalocyanines. These modifications in the structure of subphthalocyanines have been performed with the aim of demonstrating unique properties originating from the bowl-shaped C 3v-symmetric structure as well as the electronic structure delineated by the 14À-electron conjugated system on the curved molecular surface. The possible structural modifications surveyed in this feature article and their concomitant properties will provide important future guidelines to the design of subphthalocyanine-based functional molecules, considering the fact that subphthalocyanines have recently been attracting considerable attention as potential candidates in the field of optoelectronics and molecular electronics. © The Partner Organisations 2014..
46. Soji Shimizu, Yu Haseba, Mariko Yamazaki, Genji Kumazawa, Nagao Kobayashi, Control of chromophore symmetry by positional isomerism of peripheral substituents, Chemistry - A European Journal, 10.1002/chem.201304043, 20, 16, 4822-4828, 2014.04, The first example of the control of porphyrinoid chromophore symmetry based on the positional isomerism of peripheral substituents has been achieved by preparing tetraazaporphyrins (TAPs) with C4h, D2h, C 2v, and Cs symmetry due to the relative arrangement of peripheral tert-butylamino and cyano groups as push and pull substituents, respectively. The four structural isomers were successfully isolated and characterized by 1H NMR spectroscopy and X-ray crystallography. The band morphology in the Q-band region varies depending on the molecular symmetry due to the significant perturbation introduced into the chromophore by the push and pull substituents. The C4h and C2v isomers exhibit a single Q band, whereas the Q bands of the D2h and Cs isomers show a marked splitting. The magnetic circular dichroism spectra indicate that the push-pull TAPs retain the properties of the 16-membered 18π-electron perimeter generally observed for porphyrinoids. Theoretical calculations have demonstrated that the perturbation introduced by the substituents lowers the D4h symmetry of the parent TAP π-conjugated system, and this results in significant spectral changes. A novel approach to the fine-tuning of the spectral properties of porphyrinoids based on changes in the chromophore symmetry is described. Symmetry control: Control of porphyrinoid chromophore symmetry based on the positional isomerism of peripheral substituents has been achieved by preparing tetraazaporphyrins (TAPs) with C4h, D2h, C2v, and Cs symmetry as a result of the relative arrangement of peripheral substituents (see figure). A new approach to the fine-tuning of the spectral properties of porphyrinoids based on changes in the chromophore symmetry is described. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim..
47. Soji Shimizu, Shota Nakano, Ayaka Kojima, Nagao Kobayashi, A core-expanded subphthalocyanine analogue with a significantly distorted conjugated surface and unprecedented properties, Angewandte Chemie - International Edition, 10.1002/anie.201310028, 53, 9, 2408-2412, 2014.02, The introduction of a seven-membered-ring unit in the place of a five-membered-ring unit in the structure of subphthalocyanine resulted in significant distortion of the bowl-shaped structure of the conjugated molecule as well as the following unprecedented properties: the preferential formation of the axially fluoro substituted species, the fluttering-dynamic-motion-induced rapid exchange of P and M enantiomers, markedly split Q-band absorption, and a clear difference in the ring-current effects arising from the convex and concave surfaces. All in a flutter: Significant distortion of the bowl-shaped structure of subphthalocyanine upon the introduction of a seven-membered ring in place of two five-membered rings (see scheme) led to unusual properties and reactivity. Fluttering-dynamic-motion-induced rapid exchange of the P and M enantiomers as well as markedly split Q-band absorption and distinct ring-current effects arising from the convex and concave surfaces were observed. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim..
48. Xu Liang, Soji Shimizu, Nagao Kobayashi, Expanded dipyrrins with electron-withdrawing substituents: Broad range of absorption in the visible region, Tetrahedron Letters, 10.1016/j.tetlet.2013.11.013, 55, 1, 256-258, 2014.01, Reaction of meso-aryl-substituted dipyrromethanes with tetracyanoethylene led to generation of a mono-tricyanovinyl-substituted species as well as an expanded dipyrrin analogue bearing both a dicyanomethylene and a tricyanovinyl substituent at the α-positions. These novel compounds exhibit absorption spectral features perturbed by the electron-withdrawing substituents. Unique protonation-induced spectral changes were also disclosed. © 2013 Elsevier Ltd. All rights reserved..
49. Kazuaki Oniwa, Soji Shimizu, Yuta Shiina, Takamitsu Fukuda, Nagao Kobayashi, A μ-oxo hetero dimer of silicon phthalocyanine and naphthalocyanine, Chemical Communications, 10.1039/c3cc44490b, 49, 75, 8341-8343, 2013.08, A novel μ-oxo hetero dimer of silicon phthalocyanine and silicon naphthalocyanine was synthesized. Its unique optical properties, such as a single Q band, which is unusual for hetero dimer species, and solvatochromic behavior, were revealed to be better interpreted by taking interchromophore interactions into consideration. © 2013 The Royal Society of Chemistry..
50. Soji Shimizu, Yoko Yamazaki, Nagao Kobayashi, Tetrathiafulvalene-annulated subphthalocyanines, Chemistry - A European Journal, 10.1002/chem.201300709, 19, 23, 7324-7327, 2013.06, Peripheral expansion: A series of peripherally tetrathiafulvalene (TTF)-annulated subphthalocyanines was synthesized (see scheme). These compounds exhibited unique perturbed optical properties, such as a comparatively broad Q band absorption and gradual quenching of fluorescence upon increasing the number of TTF units, while electrochemical measurements revealed TTF-centered oxidation processes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim..
51. Soji Shimizu, Akito Miura, Nagao Kobayashi, Highly deformed phthalocyanine as a suitable scaffold for pristine fullerenes, CrystEngComm, 10.1039/c2ce26618k, 15, 19, 3759-3762, 2013.05, 1:1 co-crystallization of phthalocyanine with pristine C60 or C70 was achieved for the first time using a highly deformed phthalocyanine bearing phenyl substituents at α-positions. In the molecular packing diagrams of both cocrystallates, fullerene and phthalocyanine molecules are alternately arranged to form a one-dimensional array. © 2013 The Royal Society of Chemistry..
52. Ippei Sugita, Soji Shimizu, Takamitsu Fukuda, Nagao Kobayashi, Nickel and palladium complexes of seco-tribenzoporphyrazines derived from one-pot condensation of 1,3-diiminoisoindoline, Tetrahedron Letters, 10.1016/j.tetlet.2013.01.057, 54, 12, 1599-1601, 2013.03, Unexpected formation of seco-tribenzoporphyrazines from nickel- or palladium-template macrocyclization reaction of 1,3-diiminoisoindoline as a sole starting material has opened a novel access to this class of molecules. Seco-tribenzoporphyrazines exhibit strongly-split Q band absorption, basically typical of tetraazachlorin-like electronic structures, which are discussed in detail based on UV-Vis absorption and magnetic circular dichroism spectroscopies and theoretical calculations. © 2013 Elsevier Ltd. All rights reserved. © 2013 Elsevier Ltd. All rights reserved..
53. Soji Shimizu, Taku Iino, Yasuyuki Araki, Nagao Kobayashi, Pyrrolopyrrole aza-BODIPY analogues: A facile synthesis and intense fluorescence, Chemical Communications, 10.1039/c3cc38452g, 49, 16, 1621-1623, 2013.01, Pyrrolopyrrole aza-BODIPY analogues were synthesized from diketopyrrolopyrrole and heteroaromatic amines in the presence of titanium tetrachloride. These novel compounds exhibit intense absorption in the visible region and strong emission with high fluorescence quantum yields greater than 0.8. © 2013 The Royal Society of Chemistry..
54. Edwin W.Y. Wong, Akito Miura, Mathew D. Wright, Qi He, Charles J. Walsby, Soji Shimizu, Nagao Kobayashi, Daniel B. Leznoff, Gold(II) phthalocyanine revisited: Synthesis and spectroscopic properties of gold(III) phthalocyanine and an unprecedented ring-contracted phthalocyanine analogue, Chemistry - A European Journal, 10.1002/chem.201201701, 18, 39, 12404-12410, 2012.09, In 1965, gold(II) phthalocyanine (AuPc, 1) was described to be synthesized from unsubstituted 1,3-diiminoisoindoline and gold powder or AuBr. Compound 1 has been regarded as a rare example of a paramagnetic gold(II) complex. However, its chemistry, especially the oxidation state of the central gold ion, has not been previously explored due to the inherent insolubility of 1 caused by its unsubstituted structure. In our attempt to synthesize soluble AuPcs by using 5,6-di-substituted 1,3-diiminoisoindolines, gold(III) phthalocyanine chloride (3) and a gold(III) complex of an unprecedented ring-contracted phthalocyanine analogue ([18]tribenzo-pentaaza-triphyrin(4,1,1), 4) were isolated. With this discrepant result from the original literature in hand, a reinvestigation of the original AuPc synthesis by using unsubstituted 1,3-diiminoisoindoline and various gold salts (including gold powder and AuBr) was performed, finding that only unsubstituted analogues of 3 and 4 or free-base phthalocyanine were obtained. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim..
55. Tomohiro Ito, Yosuke Hayashi, Soji Shimizu, Ji Young Shin, Nagao Kobayashi, Hiroshi Shinokubo, Gram-scale synthesis of nickel(II) norcorrole: The smallest antiaromatic porphyrinoid, Angewandte Chemie - International Edition, 10.1002/anie.201204395, 51, 34, 8542-8545, 2012.08, Small is beautiful: A ring-contracted sister of porphyrin, norcorrole, has been synthesized efficiently as a stable molecule by a nickel-templated strategy. The norcorrole complex is stable but exhibits a distinct antiaromatic character according to the Hückel rule. Oxidation of the norcorrole complex provides an aromatic oxacorrole complex..
56. Soji Shimizu, Yuta Sato, Nagao Kobayashi, Para-benzihemiporphyrazine and its expanded [3 + 3]-type analogue, Chemistry Letters, 10.1246/cl.2012.702, 41, 7, 702-704, 2012.06, A novel para-benzihemiporphyrazine was synthesized from a stepwise reaction of 1,3-diiminoisoindoline and para-phenylenediamine via a linear [2 + 1]-type compound, whereas its ring-expanded [3 + 3]-type analogue was obtained from a onepot condensation reaction of the same starting materials. © 2012 The Chemical Society of Japan..
57. Soji Shimizu, Tatsuya Otaki, Yoko Yamazaki, Nagao Kobayashi, Synthesis and properties of β,β-sp3-hybridized subphthalocyanine analogues, Chemical Communications, 10.1039/c2cc30511a, 48, 34, 4100-4102, 2012.03, A β,β-sp3-hybridized subphthalocyanine analogue, dibenzosubtriazachlorin, was synthesized, and its significantly split Q band absorptions in longer and shorter wavelength regions relative to those of subphthalocyanines were revealed. The effect of benzo-annulation to a subtriazachlorin structure on the position of the split Q bands as well as the electronic structures was also investigated. © 2012 Royal Society of Chemistry..
58. Soji Shimizu, Yuki Ito, Kazuaki Oniwa, Shoma Hirokawa, Yoshiaki Miura, Osamu Matsushita, Nagao Kobayashi, Synthesis of 5,10,15-triazaporphyrins-effect of benzo-annulation on the electronic structures, Chemical Communications, 10.1039/c2cc30625e, 48, 32, 3851-3853, 2012.03, Novel triazaporphyrins were synthesized using 1,9-dibromodipyrromethene as a key starting material. These triazaporphyrins exhibit comparatively intense Soret and Q bands in the UV/vis region due to their hybrid properties between porphyrins and phthalocyanines. © 2012 The Royal Society of Chemistry..
59. Soji Shimizu, Kaoru Uemura, Hua Zhu, Nagao Kobayashi, Core-modified phthalocyanine analogues with a seven-membered ring unit in place of a five-membered ring unit, Tetrahedron Letters, 10.1016/j.tetlet.2011.11.092, 53, 5, 579-581, 2012.02, A variety of phthalocyanine analogues with a seven-membered ring unit in place of a five-membered ring unit were synthesized from aromatic dicarbonitriles bearing cyano groups at 1,4-separate positions. Based on the spectroscopic analyses and theoretical calculations, tetraazachlorine-like electronic structures of these novel compounds stemming from severe twist of the conjugation system at the seven-membered ring unit have been revealed. © 2011 Elsevier Ltd. All rights reserved..
60. Osamu Matsushita, Valentina M. Derkacheva, Atsuya Muranaka, Soji Shimizu, Masanobu Uchiyama, Evgeny A. Luk'yanets, Nagao Kobayashi, Rectangular-shaped expanded phthalocyanines with two central metal atoms, Journal of the American Chemical Society, 10.1021/ja209589x, 134, 7, 3411-3418, 2012.02, Expanded phthalocyanine (Pc) congeners with two Mo or W central metal ions and four isoindole ring moieties have been synthesized using normal Pc formation conditions in the presence of urea. The products have been characterized by electrochemistry; mass spectrometry (MS); IR, electron paramagnetic resonance (EPR), NMR, electronic absorption, and magnetic circular dichroism (MCD) spectroscopies; and X-ray analysis. The X-ray structures have rectangular C 2v symmetry and provide evidence that the central Mo atoms are linked by a single bond and coordinated by two isoindole nitrogen atoms and two nitrogen atoms from the amine moieties. The electronic absorption bands extend into the 1200-1500 nm region. This can be explained using Gouterman's four-orbital theory. The experimental NMR data and theoretical calculations provide evidence for a heteroaromatic 22-π-electron conjugation system for the ring-expanded Pc system, which satisfies Hückel's (4n + 2)π aromaticity. © 2012 American Chemical Society..
61. Yoshihiro Matano, Kazuaki Matsumoto, Hironobu Hayashi, Yoshihide Nakao, Tatu Kumpulainen, Vladimir Chukharev, Nikolai V. Tkachenko, Helge Lemmetyinen, Soji Shimizu, Nagao Kobayashi, Daisuke Sakamaki, Akihiro Ito, Kazuyoshi Tanaka, Hiroshi Imahori, Effects of carbon-metal-carbon linkages on the optical, photophysical, and electrochemical properties of phosphametallacycle-linked coplanar porphyrin dimers, Journal of the American Chemical Society, 10.1021/ja210205v, 134, 3, 1825-1839, 2012.01, 5-(Diphenylphosphanyl)-10,15,20-triarylporphyrins (meso- phosphanylporphyrins) underwent complexations with palladium(II) and platinum(II) salts to afford phosphapalladacycle- and phosphaplatinacycle-fused coplanar porphyrin dimers, respectively, via regioselective peripheral β-C-H activation of the meso-phosphanylporphyrin ligands. The optical and electrochemical properties of these metal-linked porphyrin dimers as well as their porphyrin monomer/dimer references were investigated by means of steady-state UV-vis absorption/fluorescence spectroscopy, cyclic and differential pulse voltammetry, time-resolved spectroscopy (fluorescence and transient absorption lifetimes and spectra), and magnetic circular dichroism spectroscopy. All the observed data clearly show that the palladium(II) and platinum(II) linkers play crucial roles in the electronic communication between two porphyrin chromophores at the one-electron oxidized state and in the singlet-triplet intersystem-crossing process at the excited state. It has also been revealed that the C-Pt-C linkage makes more significant impacts on these fundamental properties than the C-Pd-C linkage. Furthermore, density functional theory calculations on the metal-linked porphyrin dimers have suggested that the antibonding dπ-pπ orbital interaction between the peripherally attached metal and adjacent pyrrolic β-carbon atoms destabilizes the highest occupied molecular orbitals of the porphyrin π-systems and accounts for the observed unique absorption properties. On the basis of these experimental and theoretical results, it can be concluded that the linear carbon-metal-carbon linkages weakly but definitely perturb the optical, photophysical, and electrochemical properties of the phosphametallacycle-linked coplanar porphyrin dimers. © 2011 American Chemical Society..
62. Soji Shimizu, Shota Nakano, Takahisa Hosoya, Nagao Kobayashi, Pyrene-fused subphthalocyanine, Chemical Communications, 10.1039/c0cc01877e, 47, 1, 316-318, 2011.12, A pyrene-fused subphthalocyanine synthesized from a reaction of 2,7-di-tert-butyl-4,5,9,10-tetracyanopyrene and tetrafluorophthalonitrile exhibits red-shifted Q-band absorption and a unique linear arrangement in the solid state caused by a π-π stacking interaction. The concave conjugation of the SubPc moiety and the planar conjugation of the pyrene moiety enhanced its co-crystallization with C60 molecules. © 2010 Royal Society of Chemistry..
63. Min Chul Yoon, Pyosang Kim, Hyejin Yoo, Soji Shimizu, Taro Koide, Sumito Tokuji, Shohei Saito, Atsuhiro Osuka, Dongho Kim, Solvent- and temperature-dependent conformational changes between hückel antiaromatic and möbius aromatic species in meso-trifluoromethyl substituted [28]hexaphyrins, Journal of Physical Chemistry B, 10.1021/jp207731k, 115, 50, 14928-14937, 2011.12, We investigated the photophysical properties of figureeight- like meso-hexakis(trifluoromethyl) [26]- and [28]hexaphyrins- (1.1.1.1.1.1) denoted as TFM26H and TFM28H, respectively, using steady-state and time-resolved spectroscopy along with theoretical calculations to explore their electronic and magnetic natures depending on their molecular aromaticity. TFM26H exhibited a well-resolved absorption feature and intense fluorescence, both of which were neither solvent- nor temperature-dependent. These optical properties were in agreement with its Hückel's [4n + 2] aromaticity as observed in typical aromatic porphyrinoids. The S1-state lifetime of ̃50 ps for TFM26H in solution was shorter than those in planar aromatic hexaphyrins (>100 ps) presumably due to nonplanar figure-eight geometry of TFM26H. However, TFM28H exhibited remarkable changes in solvent- and temperature-dependent absorption spectra as well as excited-state lifetimes indicating that a dynamic equilibrium occurs between the two conformational species. With the help of quantum mechanical geometry optimization and vertical excitation energy calculations, we found that the figure-eight double-sided conformer observed in the solid-state and single-sided distorted one could be the best candidates for the two conformers, which should be Hückel antiaromatic and Möbius aromatic species, respectively, based on their optical characteristics, molecular orbital structures, and excited-state lifetimes. Conformational dynamics between these two conformers of TFM28H was scrutinized in detail by temperature-dependent 1H NMR spectra in various solvents, which showed that the conformational equilibrium was quite sensitive to solvents and that a conformational change faster than the NMR time-scale occurs even at 173 K. © 2011 American Chemical Society..
64. Soji Shimizu, Akito Miura, Samson Khene, Tebello Nyokong, Nagao Kobayashi, Chiral 1,2-subnaphthalocyanines, Journal of the American Chemical Society, 10.1021/ja2052667, 133, 43, 17322-17328, 2011.11, Following the first suggestion of inherent molecular chirality in asymmetrically substituted subphthalocyanines by Torres and co-workers in 2000, elucidation of the relationship between structure and chirality has become an important issue. However, separation of the enantiomers has been prevented by the low solubility of the molecules synthesized to date, and it has not been possible to link the CD signs and intensities to their absolute structures. Recently, we observed that 1,2-subnaphthalocyanines possess two diastereomers with respect to the arrangement of the naphthalene moieties and that these novel chiral molecules exhibit moderate solubility in common organic solvents. This has enabled us to separate all of the diastereomers and enantiomers. The two diastereomers have been completely characterized by NMR spectroscopy and X-ray diffraction analysis. The absorption and magnetic circular dichroism spectra, together with theoretical calculation, reveal a small variation in the frontier molecular orbitals of the 1,2-subnaphthalocyanines compared with conventional subphthalocyanines, except for destabilization of the HOMO-3, which results in a characteristic absorption in the Soret band region. The chirality of 1,2-subnaphthalcyanines, including the CD signs and intensities, is discussed in detail for the first time with enantiomerically pure molecules whose absolute structures have been elucidated by single-crystal X-ray diffraction analysis. © 2011 American Chemical Society..
65. Hua Lu, Soji Shimizu, John MacK, Zhen Shen, Nagao Kobayashi, Synthesis and spectroscopic properties of fused-ring-expanded aza-boradiazaindacenes, Chemistry - An Asian Journal, 10.1002/asia.201000641, 6, 4, 1026-1037, 2011.04, A series of fused-ring-expanded aza-boradiazaindacene (aza-BODIPY) dyes have been synthesized by reacting arylmagnesium bromides with phthalonitriles or naphthalenedicarbonitriles. An analysis of the structure-property relationships has been carried out based on X-ray crystallography, optical spectroscopy, and theoretical calculations. Benzo and 1,2-naphtho-fused 3,5-diaryl aza-BODIPY dyes display markedly red shifted absorption and emission bands in the near-IR region (>700a nm) due to changes in the energies of the frontier MOs relative to those of 1,3,5,7-tetraaryl aza-BODIPYs. Only one 1,2-naphtho-fused aza-BODIPY of the three possible isomers is formed due to steric effects, and 2,3-naphtho-fused compounds could not be characterized because the final BF 2 complexes are unstable in solution. The incorporation of a N(CH3)2 group at the para-positions of a benzo-fused 3,5-diaryl aza-BODIPY quenches the fluorescence in polar solvents and results in a ratiometric pH response, which could be used in future practical applications as an NIR "turn-on" fluorescence sensor. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim..
66. Soji Shimizu, Hua Zhu, Nagao Kobayashi, Azepiphthalocyanine—an unprecedented large twist of a π-conjugation system upon core-modification with a seven-membered ring unit, Chemical Communications, 10.1039/c0cc05276k, 47, 11, 3072-3074, 2011.03, Aromatic dicarbonitrile bearing cyano groups in a 1,4-relationship was utilized for a phthalocyanine synthesis to give azepiphthalocyanine having a seven-membered ring unit instead of a five-membered ring unit. This molecule exhibits a significantly twisted structure and large splitting of the Q band absorption, indicative of its azachlorin-like conjugation system. © 2011 Royal Society of Chemistry..
67. Hua Zhu, Soji Shimizu, Nagao Kobayashi, Subazaphenalenephthalocyanine: A subphthalocyanine analogue bearing a six-membered ring unit, Angewandte Chemie - International Edition, 10.1002/anie.201003929, 49, 43, 8000-8003, 2010.10, At the core: A novel core-modified subphthalocyanine analogue has been synthesized (see structure; Cl green, red O, blue N). This molecule comprises a six-membered ring unit in place of a five-membered ring unit and exhibits unique spectroscopic (see plot) and electrochemical properties originating from the azaphenalene-containing 14π-electron conjugation system. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim..
68. Soji Shimizu, Hua Zhu, Nagao Kobayashi, Azaphenalene phthalocyanines: Phthalocyanine analogues with sixMembered-ring units instead of five-membered-ring units, Chemistry - A European Journal, 10.1002/chem.201000642, 16, 36, 11151-11159, 2010.09, Mixed-condensation reaction of 1,8-naphthalenedicarbonitrile and a 4,5-disubstituted phthalonitrile provided a series of phthalocyanine (Pc) analogues with azaphenalene (AP) moieties in place of the isoindole moieties. Monosubstituted species, APPc, and the two structural isomers of disubstituted species, adj-AP2Pc and oppAP2Pc, were successfully isolated by gel-permeation chromatography on HPLC apparatus. Their structures were elucidated by 1H NMR spectroscopy and X-ray crystallographic analysis. Replacement of the isoindole moieties with azaphenalene moieties created six-membered-ring units in the core and caused distortion of the molecular structures. The Q-band absorption shifted to the red upon an increase in the number of azaphenalene units; the shape of the absorption spectra depended on the molecular symmetries. APPc and opp-AP2Pc showed a large splitting of the Q band, whereas adjAP2Pc exhibited a single broad Q band. These changes in the absorption spectra, as well as the unique electronic structures, are discussed in detail, based on magnetic circular dichroism spectra, electrochemical measurements, and density functional theory calculations. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim..
69. Ryu Sakamoto, Shohei Saito, Soji Shimizu, Yasuhide Inokuma, Naoki Aratani, Atsuhiro Osuka, Meso-trifluoromethyl-substituted subporphyrin from ring-splitting reaction of meso-trifluoromethyl-substituted [32]Heptaphyrin(1.1.1.1.1.1.1), Chemistry Letters, 10.1246/cl.2010.439, 39, 5, 439-441, 2010.03, meso-Trifluoromethyl-substituted subporphyrin was obtained through an extrusion reaction from meso-trifluoromethyl-substituted heptaphyrin( 1.1.1.1.1.1.1) upon combined metallation of Cu(II) and B(III) ions. The subporphyrin exhibited the most blue-shifted Soret-like absorption band among those ever prepared. © 2010 The Chemical Society of Japan..
70. Wadzanai Chidawanyika, John MacK, Soji Shimizu, Nagao Kobayashi, Tebello Nyokong, Effect of peripheral fused ring substitution on the optical spectroscopy and electronic structure of metal phthalocyanine complexes, Journal of Porphyrins and Phthalocyanines, 10.1142/S1088424609001339, 13, 10, 1053-1062, 2009.10, In this paper the impact of peripheral substitution with a strongly withdrawing fused ring group on the optical spectroscopy of a metal phthalocyanine complex is analyzed. We report the synthesis of [9 (or 10), 16 (or 17), 23 (or 24)-tri-tert-butylimidophthalocyaninato]zinc(II) (ZnttbIPc), which should eventually prove to be a useful precursor for forming dimeric compounds. The electronic structure is analyzed through a detailed analysis of the UV-visible absorption and magnetic circular dichroism spectra and time-dependent density functional theory calculations. Other than a marked splitting of the Q band, the spectrum is broadly similar to that of ZnPc in terms of the main π → π* electronic bands. The vibrational bands differ markedly in the Q band region when an imido group is added to ligand periphery, relative to what is observed in the case of zinc mononaphthotribenzotetraazaporphyrin (Zn3B1N) with an additional fused benzene ring. The absorption and emission spectra lack mirror symmetry as is the case with ZnPc and thus provide possible evidence for a second set of electronic origins in the Q band region arising from n → π* rather then π → π* transitions. © 2009 World Scientific Publishing Company..
71. Soji Shimizu, Atsushi Matsuda, Nagao Kobayashi, Axial ligand exchange reactions of meso-aryl subporphyrins - Axially fluoro-substituted subporphyrin and a μ-oxo dimer and trimer of subporphyrins, Inorganic Chemistry, 10.1021/ic900880b, 48, 16, 7885-7890, 2009.08, High reactivity of the boron atom of mesoaryl subporphyrins enables the introduction of a broad range of functional groups to its axial position. Axially fluoro-substituted subporphyrins were easily synthesized upon treatment of axially hydroxyl-substituted subporphyrins with BF3· OEt2. Homogeneous μ-oxo dimers of subporphyrins were formed by heating monomers in the presence of triethylamine under a high vacuum. A heterogeneous subporphyrin - phthalocyanine-subporphyrin trimer was selectively formed from the respective monomers under similar reaction conditions. Structures of these molecules were elucidated by 1H NMR spectra and a single-crystal X-ray diffraction analysis, and the interactions between neighboring chromophores in the dimeric systems were estimated from absorption and magnetic circular dichroism spectra. © 2009 American Chemical Society..
72. Jae Yoon Shin, Jong Min Lim, Zin Seok Yoon, Kil Suk Kim, Min Chul Yoon, Satoru Hiroto, Hiroshi Shinokubo, Soji Shimizu, Atsuhiro Osuka, Dongho Kim, Conformational changes of meso-Aryl substituted expanded porphyrins upon protonation: Effects on photophysical properties and aromaticity, Journal of Physical Chemistry B, 10.1021/jp8101699, 113, 17, 5794-5802, 2009.04, meso-Hexakis(pentafluorophenyl) [30]heptaphyrin(1.1.1.1.1.1.0) and mew-hexakis(pentafluorophenyl) [38]non-aphyrin( 1.1.0.1.1.0.1.1.0) have been investigatwith a particular focus on their photophysical properties affected by protonation with acids using steady-state and time-resolved spectroscopic measurements along with femtosecond Z-scan method. It was found that the smaller Stokes shift and longer excsinglet/triplet state lifetimes of protonated [30]heptaphyrin and [38]nonaphyrin compared to their distorted neutral counterparts are strongly associated with the rigid and planar molecular structures. Much larger two photon absorption cross-section vof protonated [30]heptaphyrin and [38]nonaphyrin (6300 and 6040 GM) than those of their neutral forms (1350 and 1300 GM) also reflect the enhanced rigidity and planarity as well as aromaticity. In parallel with this, the nucleus-independent chemical (NICS) values of protonated forms exhibit large negative values, -14.3 and -11.5 ppm for [30]heptaphyrin and [38]nonaphyrin, respectively, at central positions. Thus we have demonstrated the structure-property relationships between molecular planarit, photophysical properties, and aromaticity of expanded porphyrins upon protonation based on our experimental and theoretical investigations. This study also promises a possibility of structural control of expanded porphyrins through protonation in which molecular flexibilities of expanded porphyrins lead to distorted structures especially as the number of pyrrole rings increases. © 2009 American Chemical Society..
73. Valentina F. Donyagina, Soji Shimizu, Nagao Kobayashi, Evgeny A. Lukyanets, Synthesis of N,N-difluoroboryl complexes of 3,3′-diarylazadiisoindolylmethenes, Tetrahedron Letters, 10.1016/j.tetlet.2008.08.026, 49, 42, 6152-6154, 2008.10, N,N-Difluoroboryl complexes of 3,3′-diarylazadiisoindolylmethenes were synthesized by the reaction of BF3·OEt2 and 3,3′-diarylazadiisoindolylmethenes, which were easily prepared from a reaction between phthalonitrile and aryl Grignard reagents. These novel dyes exhibit strong absorption in the visible region and intense fluorescence in the vis/NIR region. Their synthesis, characterization, and optical properties are reported in this Letter. © 2008 Elsevier Ltd. All rights reserved..
74. Elena A. Makarova, Soji Shimizu, Atsushi Matsuda, Evgeny A. Luk'yanets, Nagao Kobayashi, meso-Aryl tribenzosubporphyrin - A totally substituted subporphyrin species, Chemical Communications, 10.1039/b801712c, 18, 2109-2111, 2008.04, meso-Aryl tribenzosubporphyrin was synthesized by a self-condensation of 3-benzalphthalimidine and by a condensation of phthalimide with phenylacetic acid using boric acid as a template; the compounds derived were characterized based on a wide range of spectroscopic and electrochemical methods. © The Royal Society of Chemistry..
75. Soji Shimizu, Won Seob Cho, Jonathan L. Sessler, Hiroshi Shinokubo, Atsuhiro Osuka, meso-Aryl substituted rubyrin and its higher homologues: Structural characterization and chemical properties, Chemistry - A European Journal, 10.1002/chem.200701909, 14, 9, 2668-2678, 2008.03, meso-Aryl substituted rubyrin ([26]hexaphyrin(1.1.0.1.1.0)) 2 and a series of rubyrin-type large expanded porphyrins were obtained from a facile one-pot oxidative coupling reaction of meso-pentafluorophenyl substituted tripyrrane 1. The structures of two of the resulting products were determined by single-crystal X-ray diffraction analysis. Whereas [52]dodecaphyrin-(1.1.0.1.1. 0.1.1.0.1.1.0) 4 takes a symmetric helical conformation, the larger species, [62]pentadecaphyrin-(1.1.0.1.1.0.1.1.0.1.1.0.1.1.0) 5, adopts a nonsymmetric distorted conformation in the solid state that contains an intramolecular helical structure. The ability of rubyrin 2 to act as an anion receptor in its diprotonated form (2.2H+) was demonstrated in methanolic solutions. Oxidation of 2 with MnO2 gave [24]rubyrin 6, a species that displays antiaromatic characteristics. [26]Rubyrin 2 and [24]rubyrin 6 both underwent metallation when reacted with Zn-(OAc)2 to give the corresponding biszinc(II) complexes 7 and 8 quantitatively without engendering a change in the oxidation state of the ligands. As a result, complexes 7 and 8 exhibit aromatic and antiaromatic character, respectively. NICS calculation on these compounds also supported aromaticity of 2 and 7, and antiaromaticity of 6 and 8. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA..
76. Shigeki Mori, Soji Shimizu, Ji Young Shin, Atsuhiro Osuka, Group 12 metal complexes of [26]hexaphyrin(1.1.1.1.1.1), Inorganic Chemistry, 10.1021/ic7004216, 46, 11, 4374-4376, 2007.05, Metalation of meso-hexakis(pentafluorophenyl)-substituted [26]-hexaphyrin(1.1.1.1.1.1) (1) has been explored with group 12 metal ions Zn(II), Cd(II), and Hg(II). Zn(II) and Cd(II) ions afforded dinuclear gable-shaped complexes 2 and 3 in good yields, while Hg(II) ion provided bis-Hg(II) and mono-Hg(II) planar complexes (4 and 5) via C-H bond cleavage. © 2007 American Chemical Society..
77. Yiho Kamimura, Soji Shimizu, Atsuhiro Osuka, [40]Nonaphyrin(1.1.1.1.1.1.1.1.1) and its heterometallic complexes with palladium-carbon bonds, Chemistry - A European Journal, 10.1002/chem.200601304, 13, 5, 1620-1628, 2007.02, meso-Pentafluorophenyl-substituted [40]nonaphyrin-(1.1.1.1.1.1.1.1.1) 3 has been prepared by using a stepwise ring-size-selective synthesis, and has been reduced with NaBH4 to [42]nonaphyr-in(1.1.1.1.1.1.1.1.1) 5. Structurally, 3 is characterized by a figure-of-eight shape, consisting of a porphyrin-like tetrapyrrolic segment and a hexaphyr-in-like hexapyrrolic segment, whereas 5 has been found to adopt a distorted nonplanar butterfly-like shape. In the mono-metal complexes 6 and 7, a ZnII or CuII ion is bound by the porphyrin-like tetrapyrrolic segment, maintaining the overall structure of 3. Similarly to 3. complexes 6 and 7 are interconvertible with the corresponding complexes 9 and 10 through two-electron reduction with NaBH4 and oxidation with DDQ. The metal-free hexaphyrin-like segments of 6 and 7 have been shown to serve as a suitable platform for the complexation of two palladium ions, providing hetero-trinuclear metal complexes 11 (Zn II-PdII-PdII) and 13 (CuII-Pd II-PdII) in high yields, in which the Zn or Cu ion resides at the same porphyrin-like segment, and one Pd ion is bound in an NNCC fashion through double C-H bond activation while the other is bound in an NNC fashion with single C-H bond activation. Multi-metal complexes 11, 12. and 13 exhibit small electrochemical HOMO-LUMO gaps (<0.6eV). despite their nonplanar conformations. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA..
78. Zin Seok Yoon, Jung Ho Kwon, Min Chul Yoon, Mi Kyoung Koh, Su Bum Noh, Jonathan L. Sessler, Jeong Tae Lee, Daniel Seidel, Apolonio Aguilar, Soji Shimizu, Masaaki Suzuki, Atsuhiro Osuka, Dongho Kim, Nonlinear optical properties and excited-state dynamics of highly symmetric expanded porphyrins, Journal of the American Chemical Society, 10.1021/ja064773k, 128, 43, 14128-14134, 2006.11, A strong correlation among calculated Nucleus-Independent Chemical Shift (NICS) values, molecular planarity, and the observed two-photon absorption (TPA) values was found for a series of closely matched expanded porphyrins. The expanded porphyrins in question consisted of [26]hexaphyrin, [28]-hexaphyrin, rubyrin, amethyrin, cyclo[6]pyrrole, cyclo[7]pyrrole, and cyclo[8]pyrrole containing 22, 24, 26, 28, and 30 π-electrons. Two of the systems, [28]hexaphyrin and amethyrin, were considered to be antiaromatic as judged from a simple application of Hückel's [4n + 2] rule. These systems displayed positive NICS(0) values (+43.5 and +17.1 ppm, respectively) and gave rise to TPA values of 2600 and 3100 GM, respectively. By contrast, a set of congeners containing 22, 26, and 30 π-electrons (cyclo[n]pyrrole, n = 6, 7, and 8, respectively) were characterized by a linear correlation between the NICS and TPA values. In the case of the oligopyrrolic macrocycles containing 26 π-electron systems, a further correlation between the molecular structure and various markers associated with aromaticity was seen. In particular, a decrease in the excited state lifetimes and an increase in the TPA values were seen as the flexibility of the systems increased. Based on the findings presented here, it is proposed that various readily measurable optical properties, including the two-photon absorption cross-section, can provide a quantitative experimental measure of aromaticity in macrocyclic π-conjugated systems. © 2006 American Chemical Society..
79. Soji Shimizu, Naoki Aratani, Atsuhiro Osuka, Meso-trifluoromethyl-substituted expanded porphyrins, Chemistry - A European Journal, 10.1002/chem.200600158, 12, 18, 4909-4918, 2006.06, A series of meso-trifluoromethyl-substituted expanded porphyrins, including N-fused [24]pentaphyrin 3, [28]hexaphyrin 4, [32]heptaphyrin 5, [46]decaphyrin 6, and [56]dodecaphyrin 7, were synthesized by means of an acid-catalyzed one-pot condensation reaction of 2-(2,2,2-trifluoro-1-hydroxyethyl)pyrrole (1) as the first examples bearing meso-alkyl substituents. Besides these products, porphyrin 2 and two calix[5]phyrins 8 and 9 were also obtained. [28]Hexaphyrin 4 was quantitatively oxidized to [26]hexaphyrin 14 with MnO2. These expanded porphyrins have been characterized by mass spectrometry, 1H and 19F NMR spectroscopy, and UV/Vis spectroscopy. The single-crystal structures have been determined for 3, 4, 6, 7, and 14. The N-fused [24]pentaphyrin 3 displays a distorted structure containing a tricyclic fused moiety that is similar to those of mejo-aryl-substituted counterparts, whereas 8 and 9 are indicated to take roughly planar conformations with an inverted pyrrole opposite to the sp3-hybridized meso-carbon atom. Both [28]- and [26]hexaphyrins 4 and 14 have figure-of-eight structures. Solid-state structures of the decaphyrin 6 and dodecaphyrin 7 are remarkable, exhibiting a crescent conformation and an intramolecular two-pitch helical conformation, respectively. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA..
80. Soji Shimizu, Atsuhiro Osuka, Metalation chemistry of meso-aryl-substituted expanded porphyrins, European Journal of Inorganic Chemistry, 10.1002/ejic.200501097, 7, 1319-1335, 2006.04, meso-Aryl-substituted expanded porphyrins are structural analogues of meso-aryl-substituted porphyrins. They exhibit rich and novel coordination behaviors, including multi-metal chelation due to the large cavities, spin-spin interaction arising from the proximity of metal centers, and large changes in their structural and electrochemical properties upon metalation. The recent discovery of a facile, one-pot synthesis of a series of meso-aryl-substituted expanded porphyrins enables us to investigate their metal-complexation chemistry. The aim of this Microreview is to highlight recent progress in the synthesis and characterization of metal complexes of meso-aryl-substituted expanded porphyrins. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006..
81. Venkataramanarao G. Anand, Shohei Saito, Soji Shimizu, Atsuhiro Osuka, Internally 1,4-phenylene-bridged meso aryl-substituted expanded porphyrins: The decaphyrin and octaphyrin cases, Angewandte Chemie - International Edition, 10.1002/anie.200502769, 44, 44, 7244-7248, 2005.11, Current affairs: Incorporation of a 1,4-phenylene bridge into meso aryl-substituted decaphyrin and octaphyrin has a profound impact on the structural and electronic properties of the macrocycles. Bridged decaphyrin has two oxidation states, one of which shows a rather strong diatropic ring current. X-ray crystal structure analyses reveal bridged octaphyrin possesses a p-quinodimethane unit, while bridged decaphyrin has a phenylene unit (see picture). (Chemical Equation Presented). © 2005 Wiley-VCH Verlag GmbH & Co. KGaA..
82. Tae Kyu Ahn, Jung Ho Kwon, Deok Yun Kim, Dae Won Cho, Dae Hong Jeong, Seong Keun Kim, Masaaki Suzuki, Soji Shimizu, Atsuhiro Osuka, Dongho Kim, Comparative photophysics of [26]- and [28]hexaphyrins(1.1.1.1.1.1): Large two-photon absorption cross section of aromatic [26]hexaphyrins(1.1.1.1.1.1), Journal of the American Chemical Society, 10.1021/ja050895l, 127, 37, 12856-12861, 2005.09, We have explored the electronic natures of representative expanded porphyrins, [26]- and [28]-hexaphyrins, to investigate the interplay between the aromaticity and antiaromaticity that is brought by two electron oxidation/reduction processes. The excited singlet and triplet states of [26]hexaphyrin in solution exhibit lifetimes of 125 ps and 1.8 μs, respectively, as revealed by various time-resolved spectroscopic measurements. On the other hand, [28]hexaphyrin shows faster singlet and triplet lifetimes than those of [26]hexaphyrin, which is largely in accordance with the perturbation of aromaticity due to the π electron formulation of [4n] in [28]hexaphyrins. The two-photon absorption cross-section values at 1200 nm for [26]hexaphyrins show ca. 9890 GM which is > 102 larger than those of porphyrins. The reduced TPA values of 2600 and 810 GM of [28]hexaphyrin and perfluorinated [28]hexaphyrin, respectively, match well with their relatively short excited-state lifetimes. Overall, the enhanced excited-state lifetimes for various hexaphyrins go in line with the increased TPA cross-section values and the ring planarity. © 2005 American Chemical Society..
83. Soji Shimizu, Yasuo Tanaka, Katsuyuki Youfu, Atsuhiro Osuka, Dicopper and disilver complexes of octaphyrin(1.1.1.1.1.1.1.1): Reversible hydrolytic cleavage of the pyrrolic ring to a keto-imine, Angewandte Chemie - International Edition, 10.1002/anie.200500676, 44, 24, 3726-3729, 2005.06, (Chemical Equation Presented) Metallooctaphyrin complexes: Dimetalation of perfluorinated [36]octaphyrin with copper(II) results in the hydrolytic ring opening of one of the pyrrole rings (see structure), whereas with silver ions perfluorinated [36]octaphyrin and meso-pentafluorophenyl-substituted [36]octaphyrin gave disilver(I) complexes of [34]octaphyrin. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA..
84. Shigeki Mori, Soji Shimizu, Ryuichiro Taniguchi, Atsuhiro Osuka, Group 10 metal complexes of mesoaryl-substituted [26]hexaphyrins with a metal-carbon bond, Inorganic Chemistry, 10.1021/ic050447e, 44, 12, 4127-4129, 2005.06, Nickel(II), palladium(II), and platinum(II) complexes of meso-arylsubstituted [26]hexaphyrin have been prepared and structurally characterized. In mono-metalated complexes, the metal ion is commonly bound with three pyrrolic nitrogen atoms and one pyrrolic β-carbon, whereas a bis-Pd(II) complex exhibits a unique structure involving a Pd-C α bond. These results reveal novel coordination abilities of the hexaphyrin that lead to a metal-carbon bond at either pyrrolic C β or Cα position. © 2005 American Chemical Society..
85. Shigeki Mori, Ji Young Shin, Soji Shimizu, Fumiaki Ishikawa, Hiroyuki Furuta, Atsuhiro Osuka, N-fused pentaphyrins and their rhodium complexes: Oxidation-induced rhodium rearrangement, Chemistry - A European Journal, 10.1002/chem.200401042, 11, 8, 2417-2425, 2005.04, meso-Aryl-substituted pentaphyrins were isolated in the modified Rothemund-Lindsey porphyrin synthesis as a 22-π-electron N-fused pentaphyrin ([22]NFP5) and a 24-π-electron N-fuscd pentaphyrin ([24]NFP 5), which were reversibly interconvertible by means of two-electron reduction with NaBH4 or two-electron oxidation with dichlorodicyanobenzoquinone (DDQ). Judging from 1H NMR data, [22]NFP5 is aromatic and possesses a diatropic ring current, while [24]NFP5 exhibits partial anti-aromatic character. Metalation of [22]NFP5 1 with a rhodium(I) salt led to isolation of rhodium complexes 9 and 10, whose structures were unambiguously characterized by X-ray diffraction analyses and were assigned as conjugated 24-π and 22-π electronic systems, respectively. In the rhodium(I) metalation of 1, the complex 9 was a major product at 20 °C, but the complex 10 became preferential at 55 °C. Upon treatment with DDQ, compound 9 was converted to 10 with an unprecedented rearrangement of the rhodium atom. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim..
86. Soji Shimizu, Ryuichiro Taniguchi, Atsuhiro Osuka, meso-aryl-substituted [26]hexaphyrin(1.1.0.1.1.0) and [38]nonaphyrin(1.1.0. 1.1.0.1.1.0) from oxidative coupling of a tripyrrane, Angewandte Chemie - International Edition, 10.1002/anie.200463054, 44, 15, 2225-2229, 2005.04, (Figure Presented) Acid-specific conformational changes: Protonation of meso-aryl-substituted rubyrin 1 with HCl or CF3CO2H causes different conformational changes, as revealed by specific shifts in the UV/Vis absorption bands relative to those of the free-base form (Cl-: blue shift; CF3CO2-: red shift). The distinct counteranion-dependent color changes upon addition of the acids to the "anion sensor" 1 are easily detected. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA..
87. Soji Shimizu, Venkataramanarao G. Anand, Ryuichiro Taniguchi, Ko Furukawa, Tatsuhisa Kato, Toshihiko Yokoyama, Atsuhiro Osuka, Biscopper complexes of meso-aryl-substituted hexaphyrin: Gable structures and varying antiferromagnetic coupling, Journal of the American Chemical Society, 10.1021/ja046102x, 126, 39, 12280-12281, 2004.10, The copper metalation into the hexaphyrins is accompanied by large structural changes to give four complexes exhibiting gable structures and varying antiferromagnetic couplings. Copyright © 2004 American Chemical Society..
88. Yasuo Tanaka, Wataru Hoshino, Soji Shimizu, Katsuyuki Youfu, Naoki Aratani, Norihiko Maruyama, Shizuo Fujita, Atsuhiro Osuka, Thermal Splitting of Bis-Cu(II) Octaphyrin(1.1.1.1.1.1.1.1) into Two Cu(II) Porphyrins, Journal of the American Chemical Society, 10.1021/ja031935t, 126, 10, 3046-3047, 2004.03, When heated, bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) is quantitatively split into two Cu(II) porphyrins both in solution and film states, which is accompanied by large absorption spectral changes. Copyright © 2004 American Chemical Society..
89. Soji Shimizu, Atsuhiro Osuka, meso-aryl expanded porphyrins: Synthesis, structures, and coordination chemistry, Journal of Porphyrins and Phthalocyanines, 10.1142/s1088424604000167, 8, 1-3, 175-181, 2004.03, meso-aryl expanded porphyrins, that can be regarded as real homologues of meso-tetraaryl porphyrins, were prepared by our synthetic protocol under the modified Rothemund-Lindsey conditions. This new class of molecules exhibits interesting spectral, electrochemical, and coordination properties. These promising features are emphasized, with a particular attention on the annulenic properties. Copyright © 2004 Society of Porphyrins & Phthalocyanines..
90. Masaaki Suzuki, Soji Shimizu, Ji Young Shin, Atsuhiro Osuka, Regioselective nucleophilic substitution reaction of meso-hexakis(pentafluorophenyl) substituted [26]hexaphyrin, Tetrahedron Letters, 10.1016/S0040-4039(03)00950-X, 44, 24, 4597-4601, 2003.06, Reaction of various alkoxides led to the selective replacement of the p-fluorine substituents of meso-hexakis(pentafluorophenyl) substituted [26]hexaphyrin. Reaction with isopropyl amine gave meso-hexakis(4-isopropylamino-2,3,5,6-tetrafluorophenyl) substituted [28]hexaphyrin. © 2003 Elsevier Science Ltd. All rights reserved..
91. Ryuichiro Taniguchi, Soji Shimizu, Masaaki Suzuki, Ji Young Shin, Hiroyuki Furuta, Atsuhiro Osuka, Ring size selective synthesis of meso-aryl expanded porphyrins, Tetrahedron Letters, 10.1016/S0040-4039(03)00328-9, 44, 12, 2505-2507, 2003.03, meso-Aryl expanded porphyrins were prepared in a ring size selective manner from methanesulfonic acid-catalyzed reaction of dipyrromethane and tripyrromethane with aryl aldehydes. © 2003 Elsevier Science Ltd. All rights reserved..
92. Soji Shimizu, Ji Young Shin, Hiroyuki Furuta, Rami Ismael, Atsuhiro Osuka, Perfluorinated meso-aryl-substituted expanded porphyrins, Angewandte Chemie - International Edition, 10.1002/anie.200390058, 42, 1, 78-82, 2003.01, Twisted figure-of-eight structures are found for the perfluorinated meso-aryl-substituted expanded porphyrins synthesized from 3,4-difluoropyrrole and pentafluorobenzaldehyde under modified Rothemund-Lindsey conditions. The crystal structure of the [26]hexaphyrin (see picture) consists of two almost planar tripyrrolic subunits which are tilted by approximately 60° in which a distinct alternation in the bond lengths of the π-electronic system is evident..

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