Photochromism of dihydropyridines formation and decay of coloured intermediates from 1 methyl 2,4,4,6 tetraphenyl 1,4 dihydropyride on irradiation in chloroform and acetonitrile solutions and in poly methyl methacrylate solid solution

The mechanism of the photochromic reaction of 1 methyl 2,4,4,6 tetraphenyl 1,4 dihydropyridine was studied by flash photolysis in chloroform and acetonitrile solutions and in solid solutions of poly methyl methacrylate . Photochromic species with absorption at 330, 375 shoulder , 410 and 510 nm were detected in chloroform solution immediately after the flash. The bleaching reaction in solution was monomoleculer with a rate constant of approximately 5 104 s amp; 8722;1. The reverse reaction in solid polymer solution and in the solid state was characterized by a non exponential time dependence which could be analysed in terms of a dispersive first order reaction; the time constants of the process were of the order of several seconds and several hours respectivel