Spiropyran, chromene or spirooxazine ligands: Insights into mutual relations between complexing and photochromic properties

The review describes photoswitchable molecular receptors based on spiropyran, spirooxazine, and chromene molecules. The presence of coordination centers in their structures defines the ability of such compounds to coordinate metal ions, amino acids and DNA molecules, the process being accompanied by changes in optical characteristics. Major reports describing the complex formation of spiropyrans are devoted to complexation of metal ions. Except simple substituted spiropyrans, the crown and calixarene containing spiropyrans as well as polymer composition with spiropyrans possess the effective photoswitching receptor properties. The metal complexes of spiropyrans demonstrate the photocontrolled charge and energy transfer properties. Several examples of the photochromic systems sensitive to a number of biological objects such as amino acids, proteins and DNA are described. A number of papers are devoted to the complex formation involving of spirooxazine molecules with metal ions, cyclodextrins and amino acids. The studies of benzo- and naphthopyran ligands involved mainly the incorporation of crown ether fragments into naphthopyran molecules. Very few articles describe alternative coordination functions.

► Photoswitchable molecular receptors. ► Complexation of spiropyrans with metal cations. ► Photoswitchable binding of spiropyrans with amino acids, proteins and DNA. ► Spirooxazines as photoswitchable receptors for metal cations, cyclodextrins and amino acids. ► Benzo- and naphthopyran ligands containing crown ether fragments as binding centers.