Breaking, making, and twisting of chemical bonds in gas, liquid, and nanocavities

In this Account, we recount on our studies of 1'-hydroxy-2'-acetonaphthone (HAN, a proton transfer prototype molecule) in gas, solutions, and nanocavities. The internal H-bond photoreaction in HAN leads to a keto type structure, and following its formation, an internal twisting motion gives birth to keto rotamers. Theory, temperature, and solvent effects on its photodynamics show the involvement of efficient radiationless processes in both keto structures. When HAN is caged in a cyclodextrin nanocavity, the spectroscopy, photodynamics, and issues of twisting motion are strongly affected and could be tuned: a behavior relevant to those of many chemical and biological systems.