Synthesis, photochromic behaviour and light-controlled complexation of 3,3-diphenyl-3H-benzo[f]chromenes containing a dimethylamino group or an aza-15-crown-5 ether unit

Synthesis of 3,3-diphenyl-3H-benzo[f]chromenes containing an aza-15-crown-5-ether unit or a dimethylamino group and spectrokinetic study of light-controlled complexation of these compounds with Ca2+ in acetonitrile are reported. The affinity of the azacrown chromene to Ca2+ decreases substantially upon a photoinduced ring-opening reaction. In contrast, dimethylamino chromene, which is unable to bind Ca2+ in the dark, shows a low cation-binding capacity upon UV irradiation. The spectroscopic and kinetic behaviour of the photomerocyanine isomers of these chromenes is strongly affected by complexation with Ca2+. A semi-empirical quantum-chemical study of the merocyanine isomers was applied to interpret the experimental data.