Novel photo-responsive organic spin systems: preparation and properties ofnorbornadienes and spiropyrans with TEMPO radical substituents

Several photo-responsive norbornadiene as well as spiropyran derivatives wi th TEMPO radical substituents were prepared and their light-induced structu ral changes to the corresponding quadricyclanes or merocyanine dyes and rev erse reactions to the starting materials were investigated. While the inter molecular magnetic interactions tend to be preserved in norbornadiene-quadr icyclane systems in spite of the differences of their Weiss temperatures, a switching of the intermolecular magnetic interactions was observed in the spiropyran-merocyanine systems.