Heterometallic trinuclear {Co III2LnIII} (Ln = Gd, Tb, Ho and Er) complexes in a bent geometry. Field-induced single-ion magnetic behavior of the ErIII and TbIII analogues

Abstract

Through the use of a multi-site compartmental ligand, 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl]phenol (LH₃), the family of heterometallic, trinuclear complexes of the formula [Co^III₂Ln(L)₂(μ-O₂CCH₃)₂(H₂O)₃]·NO₃·xMeOH·yH₂O has been expanded beyond Ln = Dy^III to include Gd^III (1), Tb^III (2), Ho^III (3) and Er^III (4) for 1, 3 and 4 (x = 1; y = 1) and for 2 (x = 0; y = 2). The metallic core of these complexes consists of a (Co^III–Ln^III–Co^III) motif bridged in a bent geometry resulting in six-coordinated distorted Co^III octahedra and nine-coordinated Ln^III monocapped square-antiprisms. The magnetic characterization of these compounds reveals the erbium and terbium analogues to display a field induced single-ion magnetic behavior similar to the dysprosium analogue but at lower temperatures. The energy barrier for the reversal of the magnetization of the Co^III₂Tb^III analogue is U_eff ≥ 15.6(4) K, while for the Co^III₂Er^III analogue U_eff ≥ 9.9(8) K. The magnetic properties are discussed in terms of distortions of the 4f electron cloud.