Light-driven bending of diarylethene mixed crystals

Mixed crystals composed of 1,2-bis(2-methyl-5-(p-methoxyphenyl)-3-thienyl)perfluorocyclopentene (1a) and 1,2-bis(5-methyl-2-(p-methoxyphenyl)-4-thiazolyl)perfluorocyclopentene (2a) were prepared, and their photochromic as well as light-driven bending performance was studied to reveal how shape changes of individual molecules cause the bending response. 1a and 2a molecules, having similar geometrical structures, randomly mix with each other in a single crystal. The absorption spectra of the closed-ring isomers 1b and 2b were, however, distinctly different. The difference of the spectra made it possible to discriminate the cycloreversion reactions of 1b and 2b in the mixed crystals by irradiation with 750 nm light. The bending response of the mixed crystals by the selective photoisomerization revealed that the local shape change of each molecule is additively linked to the macroscopic deformation of the crystals.