Ferromagnetic and antiferromagnetic intermolecular interactions of organic radicals, α-nitronyl nitroxides. II

Abstract

The temperature dependence of the magnetic susceptibilities and the magnetizations for the three kinds of α-nitronyl nitroxides, 2-R-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy 3-oxide [with R=phenyl (I), 3-nitrophenyl (II), 4-nitrophenyl (III)] have been measured. It is found that the intermolecular spin interaction is ferromagnetic in the crystal of III, while it is antiferromagnetic in I or II. UV–visible absorption spectra suggests the enhancements of the π-electron delocalization and the spin polarization in III in comparison with the others. The difference in the magnetic coupling between I or II and III is interpreted based on these two effects.