Synthesis and photochromic reaction kinetics of unsaturated spiropyran derivatives

The absorption spectra and decay kinetics of the ground and triplet states of merocyanine (MC) form of spiropyran vinylogs have been investigated by nanosecond laser flash photolysis techniques in toluene and ethanol. The 3MC decays to the ground state MC either by quenching with O2 or due to the intersystem crossing. Relative quantum yield of both 3MC and MC drastically decreases when the terminal polar group is separated from the indoline moiety by the CC-linker. In the presence of the CC-linker the replacement of terminal CN by CHO has no effect. The yield of 3MC and corresponding MC in ethanol is 5 times smaller than that in toluene solution.