Heterometallic trinuclear {Co super(III) sub(2)Ln super(III)} (Ln = Gd, Tb, Ho and Er) complexes in a bent geometry. Field-induced single-ion magnetic behavior of the Er super(III) and Tb super(III) analogues

Through the use of a multi-site compartmental ligand, 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl]phenol (LH sub(3)), the family of heterometallic, trinuclear complexes of the formula [Co super(III) sub(2)Ln(L) sub(2)( mu -O sub(2)CCH sub( 3)) sub(2)(H sub(2)O) sub(3)].NO sub(3).xMeOH.yH sub(2)O has been expanded beyond Ln = Dy super(III) to include Gd super(III) (1), Tb super(III) (2), Ho super(III) (3) and Er super(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 super(III)-Ln super(III)-Co super(III)) motif bridged in a bent geometry resulting in six-coordinated distorted Co super(III) octahedra and nine-coordinated Ln super(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 super(III) sub(2)Tb super(III) analogue is U sub(eff) greater than or equal to 15.6(4) K, while for the Co super(III) sub(2)Er super(III) analogue U sub(eff) greater than or equal to 9.9(8) K. The magnetic properties are discussed in terms of distortions of the 4f electron cloud.