Ground and excited state properties of chalcogenol esters: a combined theoretical and experimental study

Abstract

In this article, the synthesis and characterization of a series of chalcogenol esters 1a, 1b, 1c, 1d, 1e, 1f are described. The photophysical behavior of the esters in solution was studied using UV–vis absorption and steady‐state fluorescence emission spectroscopies. These chalcogenol esters present absorption maxima located around 332 nm and fluorescence emission maxima in the UV‐violet‐blue region. The obtained values for the Stokes' shift and the relation of the fluorescence maxima versus the solvent polarity function (Δf) from the Lippert–Mataga correlation indicate that charge transfer in the excited state occurs only for esters 1c and 1f. Theoretical calculations were also performed in order to study the geometry and charge distribution of these compounds in their ground and excited electronic states, as well as to clarify the role of the chalcogen atom in the photophysics of these compounds. Time‐dependent density functional theory calculations were performed using the CAM‐B3LYP functional with the 6‐31+G(d) basis set for geometrical optimizations and 6‐311++(2d,p) basis set for single points (absorbing and emitting structures). Solvent effects were included by the integral equation formalism of the polarizable continuum model. The large solvatochromic effect observed in the experimental emission spectra indicates that these dyes are more polar in the excited state, which was confirmed by the theoretical calculations. The computationally predicted properties are in good agreement with the experimental results and provide confirmation that the chalcogen atom plays a key role in the photophysical characteristics of the chalcogenol esters. Copyright © 2013 John Wiley & Sons, Ltd.