Synthesis, crystallography, and magnetic properties of 2-tert-butylaminoxylbenzimidazole

The title nitroxide is stable at room temperature for months. ESR spectrosc opy shows moderate spin delocalization from the nitroxide unit onto the ben zimidazole unit. The radical crystallizes in the orthorhombic Pbca space gr oup, forming columns that are joined by hydrogen bonds into a pseudo-2D mot if. Magnetic susceptibility studies of a polycrystalline sample at low temp eratures are best fit to a simple planar 2D Heisenberg model with S = 1/2 s pin sites, having a Weiss constant of theta = -4.24 K and an intraplane exc hange interaction of J/k = -1.60 K. Computational modeling of various close -contact dimeric interactions in the crystal structure suggest that the lar gest interaction in the system occurs between nearby nitroxide units relate d by a center of inversion and that this interaction is responsible for the overall antiferromagnetic interaction observed.