Synthesis, structure and magnetic properties of phosphate-bridged polynuclear copper(II) complexes

Three new phosphate-bridged copper(II) complexes, [Cu-4(H2O)(2)(phen)(4)(mu(4)-PO4)(2)(mu(2)-O)]center dot 11H(2)O (1), [Cu-4(bpy)(4)(mu(4)-PO4)(2)(mu(2)-Cl)(2)]center dot 18H(2)O (2) and [Cu-2(bpp)(4)(H2PO4)(2)](HPO4)center dot H2O (3) (phen = 1,10-phenanthroline, bpy = 2,2-bipydine and bpp = 1,3-bis(4-pyridyl)-propane), have been synthesized under ambient conditions. The tetranuclear Cu(II) butterfly cores in 1 are aggregated to 2D supramolecular layer via intermolecular pi-pi stacking interactions. In 2, the dinuclear copper units are bridged by the phosphate and Cl anion to generate centrosymmetric tetranuclear complex molecules [Cu-4(bpy)(4)(mu(4)-PO4)(2) (mu(2)-Cl)(2)], which are aggregated to 2D layers via pi-pi stacking interactions. The Cu atoms in 3 are inter-linked by a pair of bpp ligands to generate 2D (4,4) network which is through twofold '2D parallel/2D parallel' mode inclined interpenetration to induce 3D motifs. The variable temperature magnetic characterizations suggest antiferromagnetic coupling interactions with J = -9.38 and -28.03 cm (1) for 1, J = -2.41 cm (1) for 2, respectively. (C) 2012 Elsevier B. V. All rights reserved.