Heterobinuclear copper(ii)–manganese(ii) complexes behaving as three-dimensional supramolecular networks via both macrocyclic oxamido-bridges and hydrogen bonds

Abstract

Two novel oxamido-bridged heterobinuclear copper(II)–manganese(II) complexes derived from macrocylic oxamido compounds incorporating different blocking ligands were synthesized and characterized by IR and electronic spectroscopy. They are of formula [Cu(L)Mn(phen)₂](ClO₄)₂·1.5H₂O (1) and [Cu(L)Mn(ntb)](ClO₄)₂·H₂O (2), where L = 1,4,8,11-tetraazacyclotetradecane-2,3-dione, phen = 1,10-phenanthroline and ntb = tris(2-benzimidazolylmethyl)amine. The crystal structures of the two complexes have been determined and they consist of binuclear units in which the copper(II) ion is in a square-planar environment and linked to the manganese(II) ion via the exo–cis oxygen atoms of the oxamido macrocyclic ligand, with Cu⋯Mn separations of 5.421 (1) and 5.486 Å (2), respectively. The packing of the molecules along the a orientation in 2 results in open channels, which were extended into a three-dimensional hydrogen-bonded supramolecular network. The temperature dependence of the magnetic susceptibility for 1 and 2 were analyzed by means of the Hamiltonian, Ĥ = −2JŜ_MnŜ_Cu, leading to J = −14.2 and −14.7 cm⁻¹ for 1 and 2, respectively.