MS-CASPT2 analysis of the UV thermochromism of octamethyltrisilane

Abstract

We interpret the reversal of the direction of the thermochromic shift of the first absorption band of peralkylated oligosilanes as the silicon chain is extended, based on multistate complete active space second-order perturbation theory (MS-CASPT2) calculations for octamethyltrisilane, Si₃Me₈. The observed shift is attributed to the effect of b₁ distortions from ground state equilibrium geometry on vertical excited state energies and intensities. A generally contracted basis set of atomic natural orbitals (ANOs) at a ground state geometry optimized in the second-order Møller–Plesset perturbation theory (MP2) approximation with Dunning's correlation consistent triple-zeta basis set (cc-pVTZ) for the silicon atoms, the 6-31G* set for the carbon atoms and the 6-31G set for the hydrogen atoms was used.

§This paper is dedicated to Professor Michael A. Robb on the occasion of his 60th birthday.

Notes

§This paper is dedicated to Professor Michael A. Robb on the occasion of his 60th birthday.