An ab initio investigation of photoswitches adsorbed onto metal oxide surfaces: the case of donor-acceptor Stenhouse adduct photochromes on TiO2 anatase

The recent discovery of donor-acceptor Stenhouse adducts (DASAs) as a novel class of visible light activated photochromes has received considerable attention due to their high potential for original applications. Up to now, the experimental and theoretical studies have mainly focused on the intrinsic physicochemical properties and photoswitching process of these molecules, as well as on the incorporation of DASAs in multi-organized structures. In this context, we propose here the first study, by means of first-principle calculations, of DASA photochromes adsorbed onto titanium dioxide anatase surfaces. By analyzing the density of states, we show that DASAs are electronically more sensitive to the surfaces in the closed compact form than in the extended p-conjugated one, which is unusual for photochromes. This finding is also supported by an analysis of the energy band gap. A charge transfer study is performed to quantify the interactions taking place within the total systems. In addition, the impact of grafting on the optical properties is investigated using time-dependent density functional theory (TD-DFT).