Synthesis, characterization and X-ray crystal structure of a novel polyoxotungstoarsenate:: K6[{Cu(β-Ala)2(H2O)2}2{Cu4(H2O)2(AsW9O34)2}]•17H2O (β-Ala = β-alanine)

A novel polyoxotungstoarsenate, K-6[(Cu(beta -Ala)(2)(H2O)(2)}(2)(Cu-4(H2O)(2)(AsW9O34)(2)}]. 17H(2)O 1, was synthesized by the reaction of K-10[Cu-4(H2O)(2)(AsW9O34)(2)]. 20H(2)O with beta -alanine (beta -Ala). The structure of 1 was determined by single crystal X-ray diffraction and solved in the triclinic space group, P (1) over bar symmetry, with a = 11.963(2), b = 15.365(3), c = 15.914(3) Angstrom, alpha = 93.97(3)degrees, beta = 110.88(3)degrees, gamma = 101.07(3)degrees, V = 2651.8(9) Angstrom (3), Z = 1 and R1(wR2) = 0.0673(0.1628). The compound was further characterized by IR, UV, TGA, elemental analyses and magnetic measurements. The polyoxoanion framework consists of a sandwich-type polyanion [Cu-4(H2O)(2)(As-W9O34)(2)](10-) covalently linked with two [Cu(beta -Ala)(2)(H2O)(2)](2+) complex cations by two p-oxygen atoms. The results of the magnetic experiments revealed that both ferro- and anti-ferromagnetic couplings existed in 1. (C) 2001 Elsevier Science B.V. All rights reserved.