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.