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

• Published in: Journal of physical organic chemistry Vol. 27; no. 4; pp. 336 - 343
• Main Authors: da Silveira Rampon, Daniel, da Silveira Santos, Fabiano, Descalzo, Rodrigo Roceti, Toldo, Josene Maria, Gonçalves, Paulo Fernando Bruno, Schneider, Paulo Henrique, Rodembusch, Fabiano Severo
• Format: Journal Article
• Language: English
• Published: Bognor Regis Blackwell Publishing Ltd 01.04.2014; Wiley Subscription Services, Inc
• Subjects: chalcogenol esters; charge transfer; fluorescence; liquid crystals; photophysics; TD-DFT; UV-vis absorption
• ISSN: 0894-3230; 1099-1395
• DOI: 10.1002/poc.3229

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. A series of chalcogenol esters were synthesized and its spectral data obtained using UV–vis absorption and steady‐state fluorescence emission spectroscopies in solution. 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. Solvent effects were included by the integral equation formalism of polarizable continuum model. The larger 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 absorption and fluorescence emission maxima are in good agreement with the experimental results, where the chalcogen atom was shown to play a key role in the photophysical properties of the chalcogenol esters.