Design, preparation, and electronic structure of high-spin cation diradicals derived from amine-based spin-polarized donors

Amine-based donor radicals, such as dimethylamino-, diethylamino- and morpholinonitronyl nitroxides, were synthesized, and their donor abilities were examined by cyclic voltammetry. ESR spectra of the singly oxidized donor radicals showed ground state triplet signals derived from the cation radicals of these donor radicals. The result was interpreted by the presence of the ferromagnetic coupling between the generated pi -spin and the localized unpaired electron on the radical unit. According to the molecular orbital calculations, the ferromagnetic coupling between these two spins is originated from the space sharing nature between SOMO which is localized on the radical unit and SOMO' which is derived from HOMO of the donor radical upon one-electron oxidation. Therefore, the cation-radicals of these donor radicals can be regarded as a heteroanalogue of trimethylenemethane. p- and m-dimethylaminophenyl nitronyl nitroxides were synthesized in order to expand the pi -electronic structure of the donor unit, and the singly oxidized species were also found to afford triplet ESR signals. The origin of the ferromagnetic coupling of these aminophenyl nitronyl nitroxides was discussed on the same basis. Charge transfer complexes of some of the donor radicals with chloranil or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone were prepared, and the conducting and magnetic properties were examined.