The photocyclization quantum yield of 1,2-bis(2,4-dimethylthien-3-yl)perfluorocyclopentene having two benzo-15-crown-5 ethers was decreased by the addition of potassium and rubidium perchlorates, and the decrease is ascribed to the increase of the photoinactive parallel conformation ratio by the intramolecular interaction of the two crown ether moieties with a metal ion.