Biradical chelating host 2,2 '-bipyridine-6,6 '-diyl bis(tert-butyl nitroxide) showing tunable exchange magnetic coupling

The title compound was proposed as a paramagnetic host, and its chelation ability was confirmed by inclusion of a size-matching lanthanum(III) ion. The anti-configuration of the free ligand was changed to the syn configuration in the complex. The antiferromagnetic coupling was enhanced after complexation. In addition to the change of the intramolecular magnetic coupling, a superexchange mechanism is also assumed across the nitroxide-lanthanum(III)-nitroxide structure. (C) 2010 Elsevier B.V. All rights reserved.