DABCO effect on the photodegradation of photochromic compounds in spiro[indoline-pyran] and spiro[indoline-oxazine] series

Abstract

Photochromic compounds are involved in secondary oxidative reactios of photodegradation leading to the loss of their properties. The analytical studies of this process in toluene solution of both photochromic molecules, i.e. the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,2′-[3H]naphth[2,1-b]p yran] and the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]-naphth[2,1-b] [1,4]oxazine], have allowed us, by identification of the main photoproducts, to propose some mechanisms for the oxidative degradation processes which occured by radical structures or singlet oxygen. In order to prove the implication of this last species in the degradation process, we have tested the effect of a singlet oxygen quencher with experimental spectrophotometric apparatus: the 1,4-diazabicyclo[2,2,2]octan (DABCO) which exhibits an important increase of the fatigue resistance of photochromic compounds. This quantitative aspect of the DABCO effect has been completed by a qualitative degradation approach concerning a comparative analytical study by gas chromatography between degradation of photochromic compounds with and without DABCO. In those conditions we have observed a significant change in the chromatographic profiles. © 1995.