Thermal and photostability of 5′,7′-dialkoxy-5,6′-dinitro-1,3,3-trimethylspiro(lndolin-2,2′-[2H]chromenes)

Some photochromic indoline spiropyrans have been synthesized and their thermal and photostability examined in films and in solution. Introduction of the NO₂ group into the indoline moiety of the molecule stabilizes the spiropyran form in solution and in films, but blocking the NO₂ group in the pyran moiety by adjacent alkoxy groups enhances the light stability of the compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1202–1205, September, 1987.