In collaboration with Prof. Carlo Adamo of the LECIME-Equipe MSC (http://www.enscp.fr/labos/LECA/Research/site_msc/) at the Ecole Nationale de Chimie de Paris (ENSCP ParisTech) we are investigating structural and optical properties of solid photochromic systems, as well as their polymorphism. Mentioned systems find many important applications in optoelectronic, sensors, displays, actuators and so on.
Though these compounds have been studied for many years from the molecular point of view, both with theoretical and experimental methods, their solid forms still lack to be investigated, especially by computational techniques. This is due to the size and the structural complexity tipical of molecular crystals, which are governed by an interplay between H-bonds and/or dispersive interactions. Moreover, the photochromic mechanism is dependent by the polymorphism of such systems.
Our purpose is to apply accurate dispersion-corrected DFT methods which are needed to get reliable structures of the different polymorphs in the ground-state (the software CRYSTAL is used). Then, the main goal is to investigate the excited-states of optimized polymorphs by TD-DFT techniques within an embedded charge QM/QM' approach (by using the Gaussian package). This will allow to unravel the mechanism and the properties involved in the photochromic process in novel compound, and to shed light on mechanisms that are only partially explained by experiment.