Effets de substituant, d'hétéroatome et de solvant sur les cinétiques de décoloration thermique et les spectres d'absorption de photomérocyanines en série spiro[indoline‐oxazine]

Substituent, Heteroatom, and Solvent Effects on the Thermal‐Bleaching Kinetics and Absorption Spectra of Photomerocyanines Issued from Spiro[indoline‐oxazines] Quantitative information useful for the development of new photochromic systems is obtained from the study of heteroatom and substituent effects on the thermal‐bleaching kinetics and the absorption spectra of the photomerocyanines issued from spiro[indoline‐oxazines]. The effect on photochromic properties of the presence of N‐atoms either in the dimethine bridge or in the aromatic rings has been investigated through the comparison of spiro[indoline‐naphthopyrans] C with spiro[indoline‐naphthoxazines] A and with spiro[indoline‐quinolinoxazines] B. Besides the occurrence of biexponential thermal‐bleaching kinetics in non‐polar solvents is observed: a tentative explanation for this observation is given which involves the formation, in either sequential or parallel steps, of energetically distinct stereoisomers of the opened form.