Construction and photoswitching properties of fluorescent diarylethenes

Four novel fluorescent diarylethenes have been designed and synthesized. They showed excellent ring-opening and ring-closing photoisomerization properties with UV/Vis irradiation. It is found that both the ring-open and the ring-closed isomers have similar fluorescence emission, which is different from the known fluorescent diarylethenes for which the ring-open isomers exhibited strong fluorescence emission whereas the ring-closed isomers had no or weak fluorescence emission. It is also found that both the structural and the electronic properties of the substituent groups have a great influence on the absorption and emission of photochromic diarylethenes.