Formation of molecular H- and J-stacks by the spiropyran-merocyanine transformation in a polymer matrix

Kinetic and spectral properties of merocyanine dyes, formed on irradiation of spiropyran dissolved in a polymer matrix, depend on the spiropyran concentration. The observed properties are explained by a model in which the merocyanine molecules form molecular H-stacks. A method for formation of molecular J-stacks in the polymer matrix was also developed. Stabilization of the merocyanine dye in the J-stacks completely prevents the conversion back to spiropyran.