Tert-butyl 2-pyridyl nitroxide available as a paramagnetic chelate ligand for strongly exchange-coupled metal-radical compounds

Exchange coupling strength of tert-butyl 2-pyridyl nitroxide (2pyNO), used as a paramagnetic chelate ligand for strongly exchange-coupled metal-radical compounds were observed. A precursory hydroxylamine (2pyNOH) was prepared from 2-bromopyridine and 2-methyl-2-nitrosobutane via the conventional organo-lithium method. Crude 2pyNO, obtained from oxidation of 2pyNOH with Ag20, was introduced to a subsequent complexation without isolation by using a stoichiometric amount of nickel(II) and copper(II) perchlorates. The spin is polarized from the NO group onto the pyridine, leading to magnetic coupling in an intermolecular fashion. It was observed that the complexes are sufficiently stable during storage under ambient conditions for several months. The intermolecular antiferromagnetic coupling observed seems consistent with these intermolecular contacts.