Photoreactions of photochromic 1-(2,5-dimethyl-3-furyl)-1-fluoren-9-ylidene-ethane and related compounds
1-(2,5-Dimethyl-3-furyl)-1-fluoren-9-ylideneethane and its 3-thienyl analogue, in the crystalline state and in poly(propylene isophthalate) glass, changed from pale yellow to deep blue on irradiation at 366 nm; this change is reversed on exposure to white light. In solution, the title compound was photorearranged quantitatively into 1,3-dimethylfluoranthen-2-ylpropan-2-one on exposure to u.v. light. The photochromism and photoreactions of related compounds are described.