Diarylperfluorocyclopentenes having 2-isopropyl-5-phenylthiophene and 2-isopropyl-1-benzothiophene aryl groups underwent thermally reversible photochromism in solution. The photogenerated colored closed-ring isomers returned to the initial colorless open-ring isomers above 60 degreesC. The activation energies of the thermal cycloreversion were estimated to be 118 and 132 kJ/mol for the thiophene and benzothiophene derivatives, respectively.