STRUCTURE AND DYNAMICS OF THE SILACYCLOBUTANE RADICAL-CATION, STUDIEDBY AB-INITIO AND DENSITY-FUNCTIONAL THEORY AND ELECTRON-SPIN-RESONANCE SPECTROSCOPY

The geometric structure, the proton isotropic hyperfine coupling const ants and temperature dependence of the isotropic hyperfine coupling co nstants have been investigated for the silacyclobutane radical cation using Moller-Plesset perturbation theory to second order, the coupled cluster approximation and density functional theory, The temperature d ependence of the hyperfine coupling constants is explained employing a one-dimensional model for the description of the ring puckering motio n. For the geometrical structure the study supports conclusions made i n earlier work based on the measurements of the temperature dependence of the electron spin resonance (ESR) spectra, e.g. the silacyclobutan e radical cation possesses an asymmetrically distorted C-1 structure i n which one of the Si-C bonds is considerably elongated, and the ring is puckered. A reassignment of part of the ESR spectrum is obtained on the basis of the theoretical results in combination with experimental measurements of the low temperature dynamical behaviour. (C) 1997 Ame rican Institute of Physics.