Synthesis, crystal structure and magnetic behaviour of the new linear copper(II) tetranuclear compound [Cu-4(mu(2)-AcO)(6)(AcO)(2)(DPQ)(2)] (DPQ = 2,3-bis(2-pyridyl)quinoxaline)

The synthesis and the crystal structure of the new linear tetranuclear comp ound [Cu-4(mu(2)-AcO)(6)(AcO)(2)(DPQ)(2)] (1) are reported, (DPQ = 2,3-bis( 2-pyridyl)quinoxaline). Crystallographic data for 1: space group C2/m, a = 9.904(8) Angstrom, b = 13.907(2) Angstrom, c = 19.700(3) Angstrom, beta = 1 02.39(3)degrees, V = 2650(2) Angstrom(3), Z = 2, R = 0.0537. The DPQ ligand is bonded to the terminal copper atoms and acts as a chelate forming a sev en-membered ring involving the N-atoms of the pyridine rings. From the magn etic susceptibility data, 1 shows strong antiferromagnetic coupling. Accord ing to the molecular structure, the experimental data were fitted to the ex pression derived from the Hamiltonian H = - 2J(1)(S1S2 + S3S4)- 2J(2)S(2)S( 3). The best fitting parameters were 2J(1) = 5.4 cm(-1), 2J(2) = - 337 cm(- 1), g = 2.20. (C) 1999 Elsevier Science S.A. All rights reserved.