Papers - KUMAGAI, Jun

Electronic Structure of Oligosilane and Polysilane Radical Cations as Studied by Electron Spin Resonance and Electronic Absorption Spectroscopy Reviewed

J. Kumagai, H. Yoshida, T. Ichikawa

J. Phys. Chem.   Vol. 99 ( 20 ) page： 7965-7969   1995.5

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The electron spin resonance (ESR) and the electronic absorption spectra of oligosilane (Si(n)R(n+1)R(n+1)', n = 2 similar to 6) radical cations in a cryogenic solid of a Freon mixture have been compared with those of poly(cyclohexylmethylsilane) and poly(methylphenylsilane) radical cations for elucidating the structure of the SOMO orbital of the radical cations or the HOMO orbitals of the neutral polysilanes, The absorption and ESR spectra of the polymer radical cations are similar to each other and also similar to those of the oligosilane radical cations, which suggests that the unpaired electron of the polymer radical cations is not delocalized all over the Si-Si main chain. The absorption spectra of the polysilane radical cations are composed of a UV and near IR bands which correspond to SOMO --> LUMO and SOMO - 1 --> SOMO, respectively. The oligosilane and the polysilane radical cations show broad isotropic ESR spectra due to hyperfine interactions with side-chain protons. Analysis of the ESR spectra shows that the unpaired electron of the polysilane radical cation is confined to only a part of the polymer chain composed of six Si atoms.

DOI： 10.1021/j100020a019

Electronec Structure of Oligosilane and Polysilane Radical Anions As Studied by Electron Spin Resonance and Electronic Absorption Spectroscopy Reviewed

J. Kumagai, H. Yoshida, H. Koizumi, T. Ichikawa

J. Phys. Chem.   Vol. 98 ( 50 ) page： 13117-13122   1994.12

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The electron spin resonance (ESR) and the electronic absorption spectra of poly(cyclohexylmethylsilane) and poly(methylphenylsilane) radical anions in a cryogenic 2-methyltetrahydrofuran solid have been compared with those of permethyloligosilanes [Si-n(CH3)(2n+2), n = 4-6] for elucidating the electronic structure of polysilane radical anions. The spectra of the polysilane radical anions are very similar to each other and also to those of the oligosilane radical anions in which an unpaired electron occupies not an antibonding sigma(not asymptotic to)(sp) orbital but a pseudo-pi(p) orbital composed of antibonding Si-Si and antibonding Si-C orbitals. The polysilane radical anions show axially symmetric ESR spectra with g(perpendicular to) = 2.0023 and g(parallel to) = 2.0064 and the electronic absorption spectra composed of UV and near-IR bands. Analysis of the ESR and the absorption spectra shows that the unpaired electron of the polysilane radical anions is not delocalized all over the polymer chain but is confined in only a part of the polymer chain, probably around the elongated Si-Si bond of a branched polymer chain.

DOI： 10.1021/j100101a005