The photo-decolourization of spiropyranes in polymer matrices

An “inverse” photo-chromism (photo-decolourization) has been found in the case of indolinospiropyranes having an electron donating substituent in 6′- and any other type of substituent in 8′-position in polar solvents and polymeric matrices. The quantum yield of the photo-decolourization in visible light has been found to increase with the spiropyrane content. Rapid spectroscopy confirmed the existence of a pigmented form in a photo-excitation of stereo-isomers.