Early Relaxation Dynamics in the Photoswitchable Complex trans-[RuCl(NO)(py)4 ]2.

The design of photoswitchable transition metal complexes with tailored properties is one of the most important challenges in chemistry. Studies explaining the underlying mechanisms are, however, scarce. Herein, the early relaxation dynamics towards NO photoisomerization in trans-[RuCl(NO)(py)4 ]2+ is elucidated by means of non-adiabatic dynamics, which provided time-resolved information and branching ratios. Three deactivation mechanisms (I, II, III) in the ratio 3:2:4 were identified. Pathways I and III involve ultrafast intersystem crossing and internal conversion, whereas pathway II involves only internal conversion.