Reaction mechanism of photochromic crystal studied by X-ray crystal structure analysis

Abstract

Reaction mechanisms of photochromic crystal based on X-ray crystal structure analysis are reviewed. Although various organic photochromic crystals have been presented so far, reaction mechanism was not always clarified because of the lack of structural information. In order to obtain three dimensional structure of molecules in crystals before and after photochromic reactions, X-ray crystal structure analysis should be made very carefully. Thanks to recent development of XRD apparatus and analysis software, molecular structure of small amount of unstable photoproducts in crystals can be analyzed. In this review, recent progress of the relationship between the reactivity of photochromic crystal and molecular packing structure in the crystals are reviewed. In addition, the novel method in controlling photochromism, i.e., in situ control of photochromism by modified crystal structure with visible light is presented.