Crystallography of molecular excited states. Transition-metal nitrosyl complexes and the study of transient species

The study of photoinduced processes in crystals is a frontier area of crystallographic research, which requires development of novel experimental and computational methods, In a series of studies, long-lived metastable states, generated upon photoirradiation of transition-metal nitrosyl complexes, have been identified as eta(2) nitrosyl and isonitrosyl linkage isomers, and their detailed geometry has been determined, Calculations using density functional theory indicate that the species correspond to minima on the ground-state potential energy surface, The time-structure of synchrotron sources opens the possibility of time-resolved studies of transient species in crystals at the atomic level, Possible strategies for such experiments are described.