Synthesis and structural characterization of nickel(II), copper(II) and zinc(II) complexes with the hexadentate ligand 2,13-bis(2-pyridylmethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0~(1.18), 0~(7.12)]docosane

摘要

The complexes [Ni(L~2)]Cl_2 centre dot 10H_2O (1), [Cu(L~2)](ClO_4)_2 centre dot 3H_2O (2), [Cu_2(L~2)(H_2O)_2Cl_2]Cl_2 (3) and [Zn(L~2)]Cl_2 centre dot 10H_2O (4) (L~2 = 2,13-bis(2-pyridylmethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0~(1.18), 0~(7.12)]docosane) have been synthesized and characterized by X-ray crystallography, electronic absorption, ~(13)C NMR and magnetic susceptiblity as well as cyclic voltammetry. The crystal structures of 1 and 4 show that the metal ion has a slightly distorted octahedral geometry with two nitrogen atoms of the pendant arms at the axial positions. However, 2 exhibits a square-planar geometry, coordinated by secondary and tertiary nitrogen donors of the macrocycle. Furthermore, 3 reveals a binuclear structure and a center of symmetry in which the each copper ion is coordinated by a distorted square-pyramidal geometry with an N_3Cl basal plane and a water molecule in the apical position. The magnetic behavior for 3 shows that a ferromagnetic interaction between the copper(II) ions is predominant at intermediate temperature and then a weaker antiferromagnetic coupling is involved at lower temperature. Cyclic voltammetric studies for 1-3 indicate that 1 undergoes quasireversible one-electron oxidation to the Ni(III) and reversible one-electron reduction to the Ni(I), 2 undergoes a irreversible one-electron reduction to the Cu(I) state, while 3 undergoes an overall quasi-reversible two-electron reduction to the binuclear Cu(I) complex.