Coumarinyl(thienyl)thiazoles: Novel photochromes with modulated fluorescence

Novel photochromic 5-(3'-coumarinyl)-4-(3 ''-thienyl)thiazoles have been synthesized. These compounds display intensive fluorescence emission in the open form A, which is modulated by light. Fluorescence intensity decreases significantly upon irradiation of A with UV-light (lambda < 400 nm) due to formation of the cyclic form B. Irradiation of B with visible light (lambda > 470 nm) promotes its opening and the recovering of fluorescence. Novel dihetarylethenes undergo photochromic modulation of fluorescence both in solution and in polymeric matrices.