Direct Observation of Various Reaction Pathways in Crystalline State Photoreactions

Abstract

The various alkyl groups bonded to the cobalt atom in (alkyl)(base)cobaloxime complex crystals are isomerized on exposure to visible light without degradation of the single crystal form. The solid-state reactions keeping the single crystal form were called crystalline-state reactions and the reaction mechanisms were explained with the concept of reaction cavity for the alkyl group. Changing the axial alkyl groups and base ligands, a variety of crystalline-state reactions were examined not only by X-rays but also by neutron diffraction. The various reaction paths were made clear from the structures of initial, intermediate and final stages of the reactions. Two recent typical examples of crystalline state reactions, the chirality inversion only by photo-irradiation and the intermediate structures in the process of photo-isomerization, are explained. The reaction rate was proved to have a positive relation with the volume of the reaction cavity. The shape of the reaction cavity well explained the mechanism of the unusual chirality inversion.