A colour sensor system based on the photo- or thermal-isomerisation of anthraisoxazoles to phenoxazinequinones

Photo- and thermal-sensitive irreversible colour sensor systems based on the isomerisation of anthraisoxazoles to the corresponding phenoxazinequinones were examined. This reaction was first reported by Gornostaev in 1979 but its application in colour sensor systems have thus far not been studied in terms of the relative rate of isomerisation in solvents and in polymer matrices. Isomerisation produced colour changes from orange to blue, and these colour changes were easily recognized in various sensor systems. The optimisation of the structures through the reaction pathways were evaluated using the MOPAC method and the rate of isomerisation was correlated with substituent effects. It was found that photoisomerisation proceeded very smoothly but the thermal process at temperatures above 100°C was accompanied by unwanted side reactions.