Crystallography and magnetism of 1-(4-[N-tert-butylaminoxyl]-2,3,5,6-tetrafluorophenyl)pyrrole

Abstract 1-(4-[ N - tert -Butylaminoxyl]-2,3,5,6-tetrafluorophenyl)pyrrole ( BNPPF4 ) was synthesized and characterized by X-ray crystallography, electron spin resonance (ESR), and magnetism. It is unusually stable by comparison to related systems. Its crystallography shows strong twisting of the nitroxide group, and dyad π-stacking that is probably assisted by fluoroarene/pyrrole interactions. There are crystallographic nitroxide chains of >5.5 A distance between nitroxides, and chains of nitroxide to tert -butyl contacts. BNPPF4 magnetic behavior is consistent with a spin-pairing model having 2 J / k  = (−)8.7 ± 0.2 K, but not with a simple 1D AFM chain model.