Photochromisme des Spiropyranes. Étude de la Colorabilité et de la Photodégradation de Dérivés Non‐Azahétérocycliques

Abstract

Study of the photodegradation and the “colorability” of non‐azaheterocyclic spiropyrans by repeated flashes showed the influence of different effects involving the heteroatom, the substituent and the concentration. Substituents in 3′, 6′ and 8′ positions of the benzopyran part are very important for stabilization of the colored open form (thermal bleaching kinetic constant), for “colorability” and photodegradation. The primary photochemical process is essentially localized in the benzopyran part but in the photomerocyanine isomer there is interaction between the two moieties. The “colorability” and the photodegradation vary inversely with concentration. All compounds present generally a bad “colorability” but also a sufficient light‐stability at high concentrations. A general scheme for the photocoloration and photodegradation of spiropyrans is also proposed.