Energy profile of formal 1,2-dyotropic rearrangement of diarylethenes

Diarylethenes with thiophene substituents belong to photoswitchable compounds (photoswitches or photochromes). Upon UV irradiation, their colorless open-ring isomers (DAE-o) convert to the colored closed-ring isomers (DAE-c), while the back reaction is induced only by visible light irradiation. A multiple photoswitching of diarylethenes usually results in irreversible photorearrangement of DAE-c to the so-called annulated isomers DAE-a, that are stable thermally and photochemically. In the present communication, structures of a series of diarylethenes as well as their isomers were optimized on the B3LYP/6-31G(d) level of theory. It was disclosed for the first time, that DAE-a destabilized relatively DAE-c by 1.71-14.00 kcal/mol. These results are important for design of photocontrollable molecules and materials, operated in the one-way (permanent manner).