Simulation of the Properties of a Photochromic Triad

To increase the contrast between the “on” and “off” states, photochromic units may be coupled together through delocalized bridges. However, such a procedure is practically limited by the impossibility to achieve the conversion of all photochromes. In this letter, we investigate the structures and properties of a dithienylethene trimer in order to apprehend its excited-state properties in the framework of a procedure combining the simulations of the electronic spectrum with time-dependent density functional theory and the analysis of the topology of the relevant molecular orbitals. Using a range-separated hybrid, this level of theory is able to perfectly reproduce the patterns of the absorption spectrum but only yields partially correct insights regarding the ring-closure of the three dithienylethene units. These theoretical simulations are a first step toward the development of more efficient molecular switches