Photochromic properties and reaction mechanism of naphthopyran

The photochromic properties and reaction mechanism of title compounds have been examined with steady method on compounds 3-phenyl-3-[3-methylbenzothio phene-2-yl]-3H-naphtho[2,1-b]pyran (1) and 3-phenyl-3-[benzofuran-2-yl]-3H- naphtho[2,1-b]pyran (2) and nanosecond laser flash photolysis techniques on compound 3-phenyl-3-[1,2-dimethylindol-3-yl]-3H-naphtho[2,1-b]pyran (3). T he influence of oxygen on transient spectra and decay kinetics of compound 3 has been investigated. Both excited singlet state and triplet state are i nvolved in the photochromic mechanism of compound 3. The influence of molec ular structure on photochromic behavior has been studied also. Decay kineti cs indicated that the lifetime of colored forms of 1 and 2 were several ord ers of magnitude longer than that of 3.