EFFECT OF SUBSTITUENTS AND ENVIRONMENT ON THE PHOTOCHROMIC PROPERTIES OF SPIROPYRANS

1',3',3'-Trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indolines] (SPs) having methoxyl groups on the indoline ring were prepared and their photochromic properties were investigated not only in organic solvents but also in films. SPs showed ''normal'' photochromism in a less polar solvent, while 'reverse'' photochromism came to be observed as the solvent polarity was increased, and SPs having more methoxyl groups tended to show reverse phochromism in less polar solvent. Linear relationship between electronic transition energy (E(MC)) of colored species and log k was observed, where k was the rate constant for coloration or decoloration. In micellar solution, lambda(max) underwent significant blue shift and no linear relationship between E(MC) and In k was observed, indicating the factors other than polarity are also operating on the isomerization processes. In film of poly(methyl methacrylate) or polyion complexes of poly(styrensulfonate)-distearyl dimethyl ammonium, normal photochromism was observed, but the rate of decoloration was considerably smaller than that observed for the decoloration in organic solvent of similar polarity, indicating the decoloration process was controlled not only by polarity but also by viscocity of the environment.