Color Prevision of Activated Forms of Photochromic Spirooxazines and Chromenes

Abstract

Different kinds of semi-empirical quantic calculations have been used to model the lower electronic transition of photomerocyanines issued from photochromic spirooxazines and chromenes. PPP-MO leads to satisfying correlations between experimental and calculated ^λmax of an extended set of compounds. This interesting result allows to predict with a good assumption the effect of a given substitution on the electronic absorption. In contrast, all valence-electrons methods gave deceptive results as well concerning the value of the ^λmax as concerning the substituent effect on the shift of this ^λmax. It is suggested that a precise study of the fundamental and excited reaction pathways of the photochromic process could bring decisive informations about the modelling of the electronic absorption of the colored forms of spirooxazines and chromenes.