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 important in association with the rapid development of optical materials. However, photochromic compounds (thermal reversible dyes on light activation) are involved in secondary oxidative photodegradation reactions leading to the loss of their photochromic properties. Variation of the rate constant of thermal ring closure (k(Delta)) during photodegradation experiments has been reported in toluene solution for a large number of photochromic molecules (spiro[indoline-naphthoxazine], spiro[indoline-naphthopyran], spiro[indoline-benzopyran] and spiro [indoline-benzoxazine]). Benzoic acid derived from the oxidation of toluene is involved in the process.