EFFECT OF PHOTODEGRADATION ON THE THERMAL BLEACHING RATE-CONSTANT OF PHOTOCHROMIC COMPOUNDS IN SPIRO [INDOLINE-PYRAN] AND SPIRO [INDOLINE-OXAZINE] SERIES

The chemistry of spiro compounds has recently become particularly impo rtant in association with the rapid development of optical materials. However, photochromic compounds (thermal reversible dyes on light acti vation) are involved in secondary oxidative photodegradation reactions leading to the loss of their photochromic properties. Variation of th e rate constant of thermal ring closure (k(Delta)) during photodegrada tion experiments has been reported in toluene solution for a large num ber of photochromic molecules (spiro[indoline-naphthoxazine], spiro[in doline-naphthopyran], spiro[indoline-benzopyran] and spiro [indoline-b enzoxazine]). Benzoic acid derived from the oxidation of toluene is in volved in the process.