Single-molecule magnet involving strong exchange coupling in terbium(iii) complex with 2,2′-bipyridin-6-yl tert-butyl nitroxide

Abstract

A novel terbium(III)-radical complex [Tb^III(hfac)₃(6bpyNO)] (Tb-6bpyNO; 6bpyNO = 2,2′-bipyridin-6-yl tert-butyl nitroxide) was synthesized. The intramolecular antiferromagnetic interaction in Tb-6bpyNO was confirmed by comparison with the magnetic properties of [Tb^III(hfac)₃(6bpyCO)] (Tb-6bpyCO; 6bpyCO = 2,2′-bipyridin-6-yl tert-butyl ketone) together with [Y^III(hfac)₃(6bpyNO)]. Tb-6bpyNO showed a hysteresis loop with negligible coersivity below 1.6 K. The dispersion of the magnetic susceptibility with an applied bias field of 2000 Oe gave the energy barrier E_a/k_B = 21.1(8) K. In contrast, Tb-6bpyCO did not behave as a single-molecule magnet, despite having practically the same crystal field.