Synthesis and characterization of syn-anti carboxylate-bridged one-dimensional copper(II) complexes with bis(2-pyridylmethyl) amino acids

Tetradentate Schiff-base carboxylate-containing ligands, bis(2-pyridylmethyl)amino-2-ethanoic acid (pmea), bis(2-pyridylmethyl)amino-3-propionic acid (pmpa) and bis(2-pyridylmethyl)amino-4-butyric acid (pmba), react with copper(II) perchlorate to give rise to the one-dimensional polymeric chain complexes {[Cu(mu-pmea)](ClO4)(H2O)-H-.}, (1), {[Cu(mu-pmpa)](ClO4)(.)2H(2)O}(n) (2) and {[Cu(mu-pmba)(H2O)](ClO4)(.)3E(2)O}(n) (3). These complexes have been characterized by X-ray crystallography, UV-Vis spectra and variable-temperature magnetic susceptibility measurements. In complexes 1-3, distorted square-pyramidal copper(II) ions are sequentially bridged by syn-anti carboxylate groups. Each of the copper(II) ions exhibit CuN3O2 coordination environments with the three nitrogen atoms of the ligand and one oxygen atom belonging to the carboxylate group of an adjacent molecule occupying the basal positions and an oxygen atom (from a carboxylate group in the case of compounds 1-2 and from a water molecule in 3) coordinated in the axial position. The electronic spectra of the complexes are significantly affected by the coordination geometry. Magnetic susceptibility measurements indicate that complexes 1 3 exhibit very weak ferromagnetic interactions. The magnetic behavior can be explained on the basis of the structural data. (C) 2004 Elsevier Ltd. All rights reserved.