The excited-state dynamics of the photomerocyanine (PMC) form originated from spirobenzopyran and the bi-functional photochromic compound spirobenzopyran-azobenzene (SpAz), containing typical photochromic molecules of spirobenzopyran (Sp) and azobenzene (Az), was investigated by picosecond time-resolved fluorescence measurements in solution at 200 K and 285 K and in polymer film at 298 K. While the fluorescence lifetimes of PMC were about twice as long as those of SpAz under all experimental conditions, both lifetimes showed similar strong dependence on viscosity rather than temperature. These results suggest the non-radiative decay to an intermediate state could be accompanied by a significant conformational change. The effect of Az moiety in this relaxation process is also discussed.

doi:10.1016/j.jphotochem.2010.09.013