Anionic Modification of the Cu-Tb Single-Molecule Magnets Based on the Compartmental Schiff-Base Ligand

By using different anions, three Cu - Tb metal complexes, namely [Cu-2(vanophen)(2)TbCl2(MeOH)(2)]Cl center dot 3MeOH (1), [Cu-2(vanophen)(2)TbCl2(MeOH)(2)]( TCNQ)(1.5)center dot 2MeOH (2), and [Cu-2(vanophen)(2)Tb-2(N-3)(6)]center dot 2MeOH (3), based on the compartmental Schiff-base ligand H(2)vanophen (H(2)vanophen=N, N'-bis(2-oxy-3-methoxybenzylidene)-1,2-phenylenediamine, TCNQ=7,7,8,8-tetracyanoquinodimethane) have been synthesized and characterized structurally and magnetically. Except for the different charge-balancing anions, complexes 1 and 2 have a very similar trinuclear [CuTbCu] structure, where the Cu.. ions are in the [N2O4] coordination pockets of the ligands, while the Tb.. ion is coordinated by all or some of the oxygen atoms from the [O-4] pocket of the ligands. The charge-balancing anion is a Cl- ion in 1, while the positive charge is balanced by one TCNQ-0.5 radical and a half of the TCNQ- radical in 2. As for complex 3, it has a tetranuclear [CuTb](2) structure, where two [CuTb] units are bridged by end-end and end-on azides. Magnetic studies revealed that both 1 and 2 are field-induced SMMs while 3 is a zero-field SMM. The energy barriers of 1 and 3 were estimated to be (11.1 +/- 0.3) cm(-1) and (20.2 +/- 0.3) cm(-1), respectively. As for complex 2, its energy barrier was lower than that of 1, which might be due to the weak magnetic interaction between the [CuTbCu] unit and the paramagnetic radical anions. CCDC: 2165235, 1; 2165236, 2; 2165237, 3.