Modeling Diarylethene Excited States with Ab Initio Tools: From Model Systems to Large Multimers

In this chapter, we provide a review of theoretical works performed with first-principle approaches focusing on the understanding, rationalization, and improvement of diarylethene photochromes. This contribution is divided into two large parts. The first is devoted to high-level theoretical calculations (e.g., multiconfigurational wavefunction approaches) along with non-adiabatic dynamic simulations, performed on model molecules. These studies deliver an accurate picture of the photochemistry, notably by allowing the characterization of conical intersections, and provide a deep understanding of the excited-state reactivity, but at the price of using simplified chemical models. In a second stage, we describe some of the investigations performed on more realistic molecules, but with less accurate theories, typically time-dependent density functional theory. These latter works yield more qualitative insights but nevertheless allow to optimize several properties of diarylethene monomers and multimers.