Angular trinuclear copper(II) complexes of N4O-donor ligand: Syntheses, crystal structures and magnetic properties

Two trinuclear copper(II) complexes of a Schiff-base type N4O-donor ligand (LH) derived from 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11-dione and 1,3-diaminopropan-2-ol are reported. Complex [Cu3L2(ClO4)4] (1) has an angular C2-symmetric trinuclear core as revealed from single-crystal X-ray diffraction studies. The terminal coppers are in square-pyramidal geometry with an N3O2 coordination environment while the central one is in octahedral geometry with an N2O4 donor environment. Complex [Cu3L2(ClO4)(N3)(H2O)](ClO4)2 · H2O (2) has an unsymmetrical trinuclear core with an intramolecular hydrogen bonding interaction between the water and azide anion coordinated to Cu(1) and Cu(3) center, respectively. All the copper centers in 2 are in square-pyramidal geometry. The average Cu⋯Cu distance between closest metal ions in both the complexes is 3.897 Å. The coordination environment of coppers in 1 approximately mimics that of multicopper oxidases in the oxidized form and the environment in 2 mimics that of the azide derivative of ascorbate oxidase. Both 1 and 2 exhibit doublet spin ground state due to strong antiferromagnetic coupling operating through the alkoxo-bridged oxygen atoms between the copper centers.