Novel aromatic N-oxyl radical based on the benzo[g]quinoline skeleton: synthesis and intermolecular ferromagnetic interaction

A novel stable organic radical, 2,2-diphenyl-1,2-dihydrobenzo[g]quinoline-N-oxyl (2), has been synthesized and structurally characterized in order to examine the ring extension effect on the known derivative, 2,2-diphenyl-1,2-dihydroquinoline-N-oxyl (1). Based on SQUID measurement, 2 exhibited a ferromagnetic interaction obeying the Bleaney–Bowers equation with 2J = +4.6 cm−1. The X-ray analysis revealed an intermolecular edge–edge association of the aryl ring and N-oxyl moiety in the crystal of 2. The bifurcated edge–edge contacts between the α-spin site (nitroxyl O atom) and the β-spin site (aryl-H atoms) are responsible for the ferromagnetic interaction of 2.