Theoretical investigation of thermally and photochemically induced haptotropic rearrangements of chromium ligands on naphthalene systems

The description of chemical reactions by means of quantum mechanical methods is an important task and gets even more challenging if excited states have to be considered. This work focuses on the haptotropic rearrangements of chromium atoms bearing three coligands which migrate on a naphthalene-like system. The reactions are either thermally or photochemically controllable and thus the systems are candidates for molecular switches. We propose a detailed reaction scheme for the investigated system. Furthermore, we provide a detailed analysis of the important steps of the reaction cycle. In comparison to previous publications, the scope of this work also involves the quantum mechanical treatment of excited states in order to describe occurring photon absorption processes in a proper way. Linear response time-dependent density functional theory calculations were carried out to describe the molecules’ responses to the external electromagnetic perturbations. The haptotropic rearrangement of chromium complexes can be induced thermally or by UV light. The energy barriers for the migration within the excited states manifold are lower than in the ground state. [Display omitted] ► Fully theoretical work on haptotropic rearrangements of chromium complexes. ► Quantum mechanical description of photon absorption processes. ► Calculations give hints for a better understanding of the mechanistic processes. ► Lower reaction energy barriers within the excited states manifold.