Photochromism of diarylethene oxazole derivatives in a single-crystalline phase

Four diarylethene derivatives (3a–6a) bearing an oxazole ring have been prepared in an attempt to construct a system that shows photochromism upon UV irradiation in a crystalline phase. The crystals (3a, 5a, and 6a) did not show photochromism in the crystalline phase. A pure single crystal of 1-(2-methyl-1-benzofuran-3-yl)-2-(5-methyl-2-phenyl-4-oxazolyl)perfluorocyclopentene (4a) shows photochromism only in a single-crystalline phase. X-ray analysis proved that 4a packs in an anti-parallel orientation, which demonstrates photochromism in a single-crystalline phase.