Synthesis, Crystallography, and Magnetic Properties of 2-<i>tert</i>-Butylaminoxylbenzimidazole

Abstract

The title nitroxide is stable at room temperature for months. ESR spectroscopy shows moderate spin delocalization from the nitroxide unit onto the benzimidazole unit. The radical crystallizes in the orthorhombic Pbca space group, forming columns that are joined by hydrogen bonds into a pseudo-2D motif. Magnetic susceptibility studies of a polycrystalline sample at low temperatures are best fit to a simple planar 2D Heisenberg model with S = 1 / 2 spin sites, having a Weiss constant of θ = −4.24 K and an intraplane exchange interaction of J / k = −1.60 K. Computational modeling of various close-contact dimeric interactions in the crystal structure suggest that the largest interaction in the system occurs between nearby nitroxide units related by a center of inversion and that this interaction is responsible for the overall antiferromagnetic interaction observed.