Photochromism of organic compounds in the crystal state

This review article deals with recent studies on organic photochromic crystals. Three basic methods for the selective preparation of photochromic crystals of Schiff bases have been proposed. The methodologies are applicable to a wide range of potential photochromic compounds; thus, further development of new types of photochromic solid systems can be expected. In this review we introduce structures and photo-properties of recently prepared photochromic organic crystals based on proton transfer as well as other photo-induced bond formation or cleavage, along with discussion on the mechanism of their photo-coloration or photo-isomerization processes.