Vibrationally resolved circular dichroism spectra of a molecule with isotopically engendered chirality

Abstract

We present a theoretical study of vibrationally resolved circular dichroism spectra, both in the adiabatic and non-adiabatic frameworks, with a full account of Franck–Condon and Herzberg–Teller vibrational contributions for the former. Model calculations have been performed on 2(R)-deuteriocyclopentanone, whose chirality is due solely to isotopic substitution. This molecule has two distinct, nearly isoenergetic, half-chair conformations in equilibrium, and its demanding nature in terms of computational accuracy makes it a perfect candidate for performing a detailed comparison between different vibronic models. Comparisons are made with experimental spectra, and we also consider temperature effects. In order to reproduce the experimental spectrum, it is necessary to consider the geometry relaxation occurring during the n → π* transition.