Grafting Spiropyran Molecular Switches on TiO2: A First-Principles Study

To explore the optoelectronic properties of spiropyran molecular switches adsorbed onto TiO2 anatase surfaces, we performed a density functional theory (DFT)/time-dependent density functional theory (TD-DFT) study considering the two isomeric forms of the photochromes anchored by both their sides. A comparison between the features of the hybrid and isolated systems is proposed to probe the adsorption effects on both subsystems. This comparison considered, on the one hand, the density of states and the alignment of the energy levels, and, on the other hand, the UV-visible spectra of these systems. We show that several electronic and optical characteristics of the hybrid systems are modulated by the open/closed state of the photochromes. These properties are also modified by the localization of the anchor group on the photochrome.