Electron spin resonance characterization of rotational isomers of the n-butane radical cation with partially deuterated methyl groups in some halogenated matrices

Abstract

Rotational isomers of n-butane cations with partly deuterated methyl groups have been studied in CH₃CCl₃, CF₂ClCFCl₂ and CFCl₃ matrices at 4.2 K and temperatures above 77 K. It is shown that the abundance ratio between different isomers depends on the temperature and the matrix. Temperature-induced oscillations of the partially deuterated methyl groups decrease the pertinent proton hyperfine splittings. The experimental data for the spin density of the n-butane radical cation are in excellent agreement with INDO calculations based on optimized geometries obtained from MNDO and ab initio calculations.