Photochromic radical compounds based on a naphthopyran system
(Matrix presented) Naphthopyran derivatives with aminoxyl substituents (4a,b) gave the corresponding open-formed isomers (5a,b) by irradiation, which could be changed back to the starting closed-formed naphthopyrans by the treatment with SiO2 as a catalyst. The tuning of intermolecular magnetic interactions between the isomer couples was found to be possible in these reversible systems.