Crystal structure and magnetic properties of an asymmetric bridged binuclear Cu(II)-complex with a macrocyclic ligand derived from 2-hydroxy-5-methyl-isophthalaldehyde and histamine

Abstract

The Cu(II) complex C 19H 26N 6O 10Cl 2Cu 2·1.5H 2O using the macrocyclic amin derived from 2-hydroxy- 5-methyl-isophthalaldehyde and histamine consists of asymmetric bridged binuclear cations having a phenolate and hydroxyl bridge. The X-ray crystal structure analysis ( a = 42.153(8), b = 18.258(3), c = 7.534(1); space group Ccc2) shows the dimeric units linked by perchlorate groups to one- dimensional infinite chains along the c-axis. The coordination polyhedra around the copper atoms are 4 + 2 and 4 + 1, respectively, including one coordinating water molecule. The magnetic susceptibility of the complex has been measured in the temperature range from 5.1 K to 313.7 K. The magnetic exchange interaction has been interpreted in terms of strong antiferromagnetic coupling within the binuclear cation. Magnetic exchange coupling along the one-dimensional chains has been neglected because of the large distance copper-perchlorate oxygen ⩾ 2.644 Å. The exchange integral has been calculated to 2 J about −516 cm −1. Structural and magnetic aspects of the title compound forming a saturated chelate system are compared to similiar compounds using Schiff base macrocyclic ligands in relation as models for the asymmetric bridging in the oxygen transport protein hemocyanin.