COLOR PREVISION OF ACTIVATED FORMS OF PHOTOCHROMIC SPIROOXAZINES AND CHROMENES

Different kinds of semi-empirical quantic calculations have been used to model the lower electronic transition of photomerocyanines issued f rom photochromic spirooxazines and chromenes. PPP-MO leads to satisfyi ng correlations between experimental and calculated lambda(max) of an extended set of compounds. This interesting result allows to predict w ith a good assumption the effect of a given substitution on the electr onic absorption. In contrast, all valence-electrons methods gave decep tive results as well concerning the value of the lambda(max) as concer ning the substituent effect on the shift of this lambda(max). It is su ggested that a precise study of the fundamental and excited reaction p athways of the photochromic process could bring decisive informations about the modelling of the electronic absorption of the colored forms of spirooxazines and chromenes.