THERMALLY REVERSIBLE PHOTOCONVERSION OF SPIROINDOLINE-NAPHTHO-OXAZINES TO PHOTOMEROCYANINES - A PHOTOCHEMICAL AND KINETIC-STUDY

In this paper, a treatment of the spectroscopic data from thermorevers ible photochromic systems is described which allows the molar absorpti on coefficient of the metastable photomerocyanine, the quantum yield o f the colour-forming reaction and the kinetic parameters of the therma l bleaching to be determined. The results obtained for five spiroindol ine-oxazines indicate that ''colourability'' on steady state irradiati on depends on the photomerocyanine molar absorption coefficient, quant um yield and bleaching rate coefficient. For the molecules investigate d, the ''colourability'' markedly depends on temperature, due to the t emperature dependence of the bleaching reaction. The results obtained are compared with literature ''colourability scales'', determined empi rically by comparison of different systems excited by pulsed light.