Copper(II) complexes of Schiff-base and reduced Schiff-base ligands: Influence of weakly coordinating sulfonate groups on the structure and oxidation of 3,5-DTBC

Abstract

The copper(II) complexes of the Schiff-base ligands H2Sams and H2Saes and the reduced Schiff-base ligands H2Sam and H2Sae formed between salicylaldehyde and aminomethanesulfonic acid or 2-aminoethanesulfonic acid (taurine) have been synthesized in moderate yields. The solid-state structures of the five dinuclear complexes, [Cu 2(Sams)2(H2O)2] (1), [Cu 2(Sam)2(H2O)2]·H 2O (2), [Cu2(Saes)2(H2O)2] ·2H2O (3), [Cu2(Sae)2]·2H 2O (4), and [Cu2(Sae)2(DMF)2] ·2DMF (5), have been determined by X-ray crystallography, showing that the CuII centers have distorted square-pyramidal geometry. The Schiff-base copper complexes 1 and 3 have hydrogen-bonded 2D sheet structures while the reduced Schiff-base complexes 4 and 5 display a 2D coordination network and a hydrogen-bonded 2D structure respectively. All these complexes have been investigated for their catecholase activity and activity measurements have been compared with those of dinuclear copper(II) complexes of similar ligands obtained with carboxylate analogues of the corresponding sulfonic acids; these studies show that 4 has significantly higher activity. Further, a strong antiferromagnetic interaction between CuII ions in dimeric complexes 1 [J = -9.04(2) cm-1], 3 [J = -272(4) cm-1), and 4 [J = -237(4) cm-1] has been observed. © Wiley-VCH Verlag GmbH & Co. KGaA, 2005.