Synthesis, crystal structure and antimicrobial properties of a copper(II) complex of an unsymmetrical tripodal ligand

Abstract

A new copper(II) complex of an unsymmetrical tripodal ligand (NN₂O222) derived from tris(2-aminoethylamine)amine (tren) by substitution of one aminoethyl group by an hydroxyethyl group has been synthesized and characterized by X-ray crystallographic methods as [(NN₂O222)Cu(ImH)](ClO₄)₂·0.5H₂O (NN₂O222 = 2-[bis(2-aminoethyl)amino]ethanol; ImH = imidazole). Crystals of the complex are orthorhombic, space group Pna2₁, with a = 29.983(10), b = 15.568(5), c = 8.127(3) Å. Two similar monometallic cations exist in the asymmetric unit and in each case the Cu(II) ion is five-coordinate with tetragonally distorted trigonal bipyramidal geometry. Variable-temperature magnetic measurements show that there is very weak antiferromagnetic interaction between the metal ions. Cyclic voltammetry indicates quasi-reversible Cu^II/Cu^I redox behavior at +44 mV vs SCE. An antimicrobial activity study found that the complex is active against Candida albican, Staphylococcus aureus, Bacillus pumilus, Klebosiella pneumoniae and Escherichia coli, but to no greater extent than Cu(ClO₄)₂·6H₂O.

Keywords:

• Tripodal ligand
• Copper(II)
• X-ray structure: Electrochemistry
• Antimicrobial behavior

Acknowledgements

This project was supported by the National Natural Science Foundation of China (No. 50372028).