Synthesis, structure, and magnetic properties of three chiral sodium-centered polynuclear copper(II) clusters with L-alanine

Abstract

By controlling the reactant proportion, three sodium-centered polynuclear octahedral copper(II)-amino acid clusters, [Na⊂{Cu6(Ala) 8(H2O)(ClO4)}]·4ClO4· 4H2O (1), Na[Na⊂{Cu6-(Ala)8(ClO 4)}]2·9ClO4·8H2O (2), and [Na⊂{Cu5(Ala)6(H2O)3}] n· 5n(ClO4)·3n(H2O) (3) (Ala = L-alanine), were synthesized. The structures were characterized by X-ray structure analysis. The structure of 1 can be described as an octahedron formed with six copper atoms in which four Cu(Ala)2 ligands bridge two axial copper ions and capture one Na+ in the center of the cage and that of 2 as an octahedral dimer that is linked by two carboxylate oxygen atoms. Complex 3 is a chain composed of incomplete octahedron [NaCu5] units linked together by two carboxylate oxygen atoms. The magnetic susceptibility measurements indicate that all three clusters are ferromagnetic overall, although the intercluster interactions may be antiferromagnetic. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.