Remarkably strong intermolecular antiferromagnetic couplings in the crystal of biphenyl-3,5-diyl bis(tert-butyl nitroxide)

Magnetic susceptibility measurements of biphenyl-3,5-diyl bis(t-butyl nitroxide) diradical showed practically diamagnetic behavior over a temperature range 1.8–300 K. The strong antiferromagnetic couplings are ascribable to intermolecular interactions whilst intramolecular coupling could not be observed. Partly bonding nature can be pointed out in the intermolecular N–O′ contacts with the distances of 2.321(2) and 2.359(2) Å, which are 23–24% shorter than the sum of the van der Waals radii. On the other hand, the N–O bond lengths of 1.303(2) and 1.294(2) Å are somewhat longer than typical values of t-butyl phenyl nitroxide radicals reported.