Magnetic study on radical-gadolinium(III) complexes. Relationship between the exchange coupling and coordination structure

Antiferro- and ferromagnetic couplings were observed in [Gd(hfac)3(2pyNO)(H2O)] and [Gd(hfac)3(HNN)2], respectively. The magnitude of the former is the largest in Gd-nitroxide complexes. An empirical relation between the exchange coupling and torsion angle Gd-O-N-C is drawn, where large torsion (>36°) favors ferromagnetic coupling.