Time-Dependent Density Functional Theory Study of Structure-Property Relationships in Diarylethene Photochromic Compounds

Abstract

Abstract. Photochromic compounds exhibit reversible transition betweenclosed and open isomeric forms upon irradiation accompanied by change in their color. The two isomeric forms differ not only in absorption spectra, but also in various physical and chemical properties and find applications as optical switching and data storage materials. In this contribution we apply Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) to predict the equilibrium geometry and absorption spectra of a benchmark set of diarylethene based photochromic compounds in open and closed forms (before and after photocyclization). Comparison of the calculated Bond Length Alternation parameters with those available from the X-ray data indicates M05-2x functional to be the best method for geometry optimization when basis set includes polarization functions. We found M05 functional accurately predicts the maximum absorption wavelength when solvent is taken into account. We recommend combined theory level TD-M05/6-31G*/PCM//M05-2x/6-31G*/PCM for prediction of geometrical and spectral parameters of diarylethene derivatives.

Plasmon–Excitation Coupling for Dithienylethene/Gold Nanoparticle Hybrid Systems: A Theoretical Study

“…The molecule and the different NPs under study are sketched in Figure . The molecule physisorbed onto the NP is a photochromic compound, belonging to the DTE family, a class of compounds well-known for its fatigue resistance and thermal stability. ,,,− The open and closed isomers involved in the photochromic mechanism are sketched in Figure a. The open form ( DTE-o ) absorbs in the UV region of the electromagnetic spectrum, while the closed form ( DTE-c ) absorbs in the visible one.…”

“…Other numerical methods like discrete dipole approximation (DDA) , or finite domain time difference (FDTD) have been used to predict the optical properties of metallic structures with various shapes such as nanorods, nanodisks, polyhedrons, star-shaped, or oval NPs. , On the other side, from the molecular point of view, time-dependent density functional theory (TD-DFT) , is recognized as an efficient ab initio theoretical tool to describe the vertical excitations of conjugated organic molecules, , allowing a good agreement with experimental UV–visible measurements for a reasonable computational effort. Within this framework, photochromic compounds have been thoroughly studied. − …”

Tuning the Photophysical Properties of Pyrene-Based Systems: A Theoretical Study

“…We introduce two geometry parameters to describe the global variations of the CÀC bond distances: (a) the mean length (d M ) as descriptive index of the relaxation or contraction of the Py ring and (b) the bond length alternation (BLA) that for linear conjugated molecules was successfully correlated with their linear and nonlinear optical properties. 55 Despite its straightforward definition in linear systems, no general definition like this has been proposed for the polycyclic aromatic hydrocarbons (PHAs) like pyrene. In this paper, we have adopted the BLA definition generally used for PAHs, which is correlated to the aromaticity index, that is, the standard deviations of the CÀC ring bonds:…”

Applications and validations of the Minnesota density functionals

“…Patel and Masunov [114,115] employed TD-DFT with the linear response formalism to include continuum solvation to calculate absorption spectra of 29 diarylethene derivatives. They found that M05-2X gave the most accurate predictions of bond length alternation (see also [116]), and M05 at M05-2X geometries gave the best agreement with experiment for spectral data of both open and closed isomers.…”