Photoinduced Linkage Isomers of Transition-Metal Nitrosyl Compounds and Related Complexes

The seminal discovery of light-induced changes in transition-metal nitrosyl complexes in the late 1970s and their identification as metastable linkage isomers almost 20 years after the initial discoveries have in recent years motivated a plethora of experimental and theoretical studies. They have raised the question of whether the linkage isomers play a role in the many crucial biological processes involving nitric oxide, which though likely, is still a subject of investigation. The linkage isomers have potential technological importance, as the change in refractive index on a molecular scale, associated with the photoinduced change in the crystals, in principle allows the design of very high capacity storage devices. This review summarizes the current knowledge in the still-developing field and includes a discussion of photoinduced metastable linkage isomers of related substances.