Diarylethene derivatives having 1,2-bis(3-n-alkyl-1-benzothiophen-2-yl)perfluorocyclopentene have been synthesized to examine their photochromic properties in solution. All the derivatives underwent photochromism in hexane. The introduction of long-chain substituents to the 3-positions of a 1-benzothiophene unit leads to longer wavelengths of the absorption band of the closed-ring isomer. However, the cyclization quantum yields of these compounds showed no increase with alkyl chain length.