Photochemistry of spiropyrans of the dithiolane series with polycondensed chromene fragments

It has been shown on the basis of determinations of the values of the quantum yields of the photocoloration of spiropyrans of the 1,3-dithiolane and benzo1,3-dithiolane series that the annelation of a benzene ring in the chromene part of the molecule results in an increase in the efficiency of photocoloration and an increase in the stability of the merocyanine forms of the compounds investigated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2504–2510, November, 1989.