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 ç 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.