Reverse Photochromism of Nitrosubstituted Bisspiropyran Based on Benzopyrroloindole

Abstract

The photochromic properties of new di- and tetranitrobisspiropyrans have been studied. Dinitrobisspiropyran solutions are characterized by direct photochromism, whereas reverse photochromism—coloration of the solution in the dark and its discoloration under the action of visible or UV light—is observed in solutions of tetranitrobisspiropyran in polar and weakly polar solvents and in polymer matrices of poly(methyl methacrylate) (PMMA) and polyvinyl butyral (PVB). The features of reverse photochromism are discussed, and a comparison with the photochromism of model nitrosubstituted monospiropyrans and dinitrobisspiropyran is carried out.