Ab initio studies of the dipole polarizabilities of conjugated molecules. Part 6. The geometry, static dipole polarizability and first hyperpolarizability of benzothiophene

Abstract

We report an ab initio study of the geometry and static dipole (hyper)polarizability of benzothiophene in its electronic ground state 1A′. We fully optimized the geometry both at the HF/3-21G ∗∗ and HF/6-31G ∗∗ levels of theory, and we present comparisons with the HF/6-31G ∗∗ thiophene geometry reported previously. We calculated the dipole (hyper)polarizabilities using an analytic coupled perturbed Hartree-Fock method, with both the STO/6-31 + G and STO/6-31G (d,p) basis sets. We analysed the average polarizability in terms of an “additive polarizabilities” scheme. We investigated the effects of electron correlation on the dipole moment and the (hyper)polarizabilities, using a fourth-order Taylor expansion of the MP2 Møller-Plesset energy and the STO/6-31 + G basis sets, which includes diffuse primitives. Taking as reference the Hartree-Fock results, these latter effects account for changes of 29% in the predicted dipole moment and between 3.30% and 5.3% in the predicted static polarizability components. The correlation effects on the first and second hyperpolarizability components are much bigger.