Publications by authors named "Shin-Ichiro Ishida"

On-surface chemical reaction has become a very powerful technique to synthesize nanostructures by linking small molecules in the bottom-up approach. Given the fact that most reactants are simultaneously activated at certain temperatures, a sequential reaction in a controlled way has remained challenging. Here, we present an on-surface synthesis of multi-block co-oligomers from trifluoromethyl (CF ) substituted porphyrin metal complexes.

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Highly twisted structures of expanded porphyrin provide a prominent basis to unravel the relationship between aromaticity and chirality. Here we report the synthesis of bis-Ge(IV) complexes of [38]octaphyrin that display rigid figure-eight structures. Two bis-Ge(IV) [38]octaphyrin isomers with respect to the stereochemistry of the axial hydroxy groups on the germanium ions were obtained and found to be aromatic.

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A peripherally strapped [28]hexaphyrin takes a rectangular conformation and exhibits antiaromatic character. A cyclophane-type dimer consisting of such [28]hexaphyrins was synthesized from hexakis(pentafluorophenyl) [26]hexaphyrin via S Ar reaction with allyl alcohol, one-pot intra- and intermolecular olefin metathesis under improved Hoveyda-Grubbs catalysis, and final reduction with NaBH . The cyclophane-type structures of [26]- and [28]hexaphyrin dimers have been revealed by X-ray analysis.

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Silicon complexation of a [38]octaphyrin (1) was accomplished by reaction with an excess amount of MeSiCl in the presence of N,N-diisopropylethylamine, thus giving an aromatic [38]octaphyrin bis(silicon) complex 2. This complex was interconvertible with an antiaromatic [36]octaphyrin congener (3) by oxidation with MnO and reduction with NaBH . Curiously, mild oxidation of 2 with ferrocenium hexafluorophosphate afforded a [37]octaphyrin bis(silicon) complex 4 as an stable radical cation that can be stored under ambient conditions in the solid state.

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[28]Hexaphyrin Ge and Sn complexes were synthesized in high yields by reactions of [28]hexaphyrin with GeCl or SnCl in the presence of triethylamine. Both complexes display distinct 28π Möbius aromatic character and possess a trigonal bipyramidal geometry at the central Ge or Sn atom. The equatorial hydroxy group of the Ge complex was smoothly exchanged with neutral nucleophiles, such as phenol derivatives and thiophenol, with retention of configuration.

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Treatment of nonaromatic N-fused [24]pentaphyrin with trichloromethylsilane in the presence of a base afforded doubly N-fused [24]pentaphyrin and its silicon complex. Addition of fluoride ion to the silicon complex led to the formation of its fluorosilicate as an unprecedented monoanionic six-coordinated Si complex of porphyrinoid. Treatment of the fluorosilicate with acid led to the recovery of the silicon complex.

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Herein, the synthesis of Möbius aromatic [28]hexaphyrin silicon complexes bearing various Si-substituents from reactions of [28]hexaphyrin 1 with suitable silicon sources in the presence of a base is reported. Si-substituents newly introduced are vinyl (4), phenyl (6), hydroxy (7), and hydride groups (8). X-ray crystallographic analysis of complexes 6 and 7 has shown trigonal bipyramidal penta-coordinated silicon atoms, which are favorable for the hexaphyrin ligands to take on smoothly twisted Möbius conformations.

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Incorporation of Si(IV) into an expanded porphyrin has been achieved for the first time. Treatment of [28]hexaphyrin 1 with CH(3)SiCl(3) and N,N-diisopropylethylamine gave Si(IV) complex 2 and its N-fused product 4 that both have Möbius aromatic nature. In both complexes, the coordinated Si atom is satisfied in a typical trigonal bipyramidal coordination.

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