Issue 19, 1999

Asymmetrically distorted structure of radical cations of ethylsilanes, studied by electron spin resonance spectroscopy, abinitio and density functional theories

Abstract

ESR spectra for the radical cations of SiEt2H2, SiEt3H, SiEt4 and SiEt2MeH, generated in halocarbon matrices by ionizing radiation at 77 K, consist of a doublet with a coupling constant of ca. 6.3 mT to a 1H nucleus. Accumulation of our data for the cations with C–Si–C bonds suggests that the cations adopt asymmetrically distorted structures with an unpaired electron largely in one of the elongated Si–C bonds and that the 1H nucleus in the “trans’' position to the bond results in the large hyperfine (hf) splitting observed. Calculations at abinitio theory and density functional theory (DFT) levels strongly support this conclusion. The reversible spectral changes, observed for SiEt2H2+ and SiEt2MeH+ in CF2BrCF2Br matrices, have been analyzed with a three-site jumping model for the internal rotation of the methyl group having the 1H nucleus assigned and a two-site jumping model for a selective bond length alternation between two adjacent Si–C bonds.

Article information

Article type
Paper

Phys. Chem. Chem. Phys., 1999,1, 4549-4554

Asymmetrically distorted structure of radical cations of ethylsilanes, studied by electron spin resonance spectroscopy, abinitio and density functional theories

K. Komaguchi, T. Marutani, M. Shiotani and A. Hasegawa, Phys. Chem. Chem. Phys., 1999, 1, 4549 DOI: 10.1039/A905143K

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