Polynuclear croconato-bridged-copper(II) complexes derived from tri- and tetra-dentate amines

Three new polynuclear bridged croconato copper(II) complexes with different dimensionality {[Cu(bedmpza)(mu(2)-C5O5)]-4H(2)O}(n) (1), {[Cu-3(aepn)(3)(mu(2)-C5O5)(mu(3)-C5O5)(H2O)](ClO4)(2)center dot 1.6H(2)O}(n) (2), and [Cu-2(dppa)(2)(mu(2)-C5O5)](ClO4)(2)center dot 2H(2)O (3) where bedmpza = bis(2-(3,5-dimethylpyrazol-1-yl)ethyl)amine, aepn = N-(2-aminoethyl)-1,3-propanediamine, dppa = N-propionamide-N,N-bis(2-pyridylmethyl)amine, and C5O52- = the croconate dianion were synthesized and structurally characterized by single crystal X-ray crystallography. In these complexes, the bridged croconato ligand displays a variety of coordination bonding modes: 1,2-bidentate-3-monodentate and 1,2-bidentate-4-monodentate in complexes 1 and 3, respectively. In complex 2, two alternative bonding modes were detected: mu(2)-bridging 1,2-,2,3-bis(bidentate) and the new mu(3)-bridging mode 1,2-(bidentate)-3,5-bis(monodentate). The magnetic susceptibilities of the complexes were investigated at variable temperatures, and all reveal weak to very weak antiferro-magnetic coupling. (C) 2012 Elsevier Ltd. All rights reserved.