Azobenzene Derivatives Carrying a Nitroxide Radical

Several trans-azobenzene derivatives carrying a nitroxide (aminoxyl) radical (2a, 6a−12a) were prepared,
and their photoisomerization reactions to the corresponding cis-isomers were investigated. Although no
fruitful results could be obtained for the photoisomerizations of the derivatives with para-subsituents
(9a−12a), the unsubstututed derivatives at the para-position (2a, 6a, 7a, 8a) were found to show
photoisomerizations by irradiation to give the corresponding cis-isomers (2b, 6b, 7b, 8b), being isolated
as relatively stable solid materials, and the change of the intermolecular magnetic interactions was
apparently observed by the structural change for each photochromic couple.