Kinetic modelling of the photochromism and photodegradation of a spiro[indoline-naphthoxazine]

The photochromism of the 1,3,3-trimethylspiro[indoline-naphthoxazine] A has been studied under continuous monochromatic irradiation (313 and 365 nm) i n liquid toluene solution at 278 K. The values of the main photochromic par ameters (quantum yields and absorption coefficients) have been determined b y kinetic modelling of absorbance (Abs) versus time curves recorded under c ontinuous irradiation We showed that the quantum yields of both photocolora tion and reversible photochemical bleaching were wavelength-dependent. Unde r 365 nm irradiation, photodegradation processes that are not sensitive to the presence of oxygen were observed. The degradation occurs either from th e direct irradiation of the closed spiro form A or from the thermal decompo sition of the open photomerocyanine form B. Under our experimental conditio ns, photochemical decomposition of the open photomerocyanine form B was neg ligible. (C) 1999 Elsevier Science S.A. All rights reserved.