Heterometallic trinuclear {Co2IIILnIII} (Ln = Gd, Tb, Ho and Er) complexes in a bent geometry. Field-induced single-ion magnetic behavior of the ErIII and TbIII analogues

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(2)(III)Ln(L)(2)(mu-O2CCH3)(2)(H2O)(3)]center dot NO3 center dot xMeOH center dot yH(2)O 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 (Co2TbIII)-Tb-III analogue is U-eff >= 15.6(4) K, while for the (Co2ErIII)-Er-III analogue U-eff >= 9.9(8) K. The magnetic properties are discussed in terms of distortions of the 4f electron cloud.