Wide-range IR spectra of diarylethene derivatives and their simulation using the density functional theory

Abstract

Diarylethenes (DAEs), promising photochromic molecular switches, undergo pericyclic reactions upon ultraviolet or visible light illumination. For this reason, most studies on DAEs employ UV–vis spectroscopies. However, also their infrared (IR) spectra are valuable, in particular, for understanding the vibrational dynamics which accompanies the relevant photoreactions. An accurate assignment of IR bands to molecular modes can be achieved through a comparison between experimental and computed theoretical spectra. Even though more sophisticated computational methods are available, the density functional theory (DFT) is usually employed for this task, because of its modest cost and versatility. Here, we have tested the ability of several DFT functionals to reproduce the wide-range, 400–3200 cm−1, IR spectra of open and closed isomers of four representative DAE molecules. We find that global and range-separated, corrected for anharmonicity by scaling factors, hybrid DFT functionals are able to reproduce the IR spectra of DAEs, however, instead of the popular B3LYP functional we propose the use of the dispersion-corrected PBE0 functional. The paper also proposes a semi-automatic method of band assignment.

Conformations of Steroid Hormones: Infrared and Vibrational Circular Dichroism Spectroscopy

“…Recently, the performance of some hybrid and double-hybrid functionals in conjunction with partially augmented double- and triple-zeta basis sets in predicting IR band frequency and intensity has been evaluated [ 69 ] where the double-hybrid functional B2PLYP shows excellent performance. In addition, several hybrid functionals were tested to reproduce the IR spectra of the open and closed isomers of four diarylethenes, and the authors recommended to use the dispersion-corrected PBE0 functional [ 70 ]. Below we tested the performance of PBE0 [ 71 ]-D3BJ/def2-TZVPD and a mixed single and double-hybrid functional method [ 72 ] (vide infra) for the IR and VCD spectra of AcO-DHEA.…”

Harmonic scale factors of fundamental transitions for dispersion-corrected quantum chemical methods

“…Despite the existence of various vibrational diagnostic bands for molecular functional groups [11,12,27] and databases of the experimental IR spectra, such as the NIST Chemistry WebBook, [28] most experimental studies of novel uncharacterized substances have to rely on quantum-chemical calculations. [5,6,8,9,[16][17][18][29][30][31][32][33] To achieve a sufficiently good agreement of quantumchemical calculations and experiment requires the application of expensive computational methods and direct inclusion of anharmonic effects. [6,8,34,35] Unfortunately, such anharmonic calculations require significant expertise and computational efforts, which make them unfeasible for many practical cases.…”