Three copper(II) complexes connected through tetradentate carboxylate linkers and bidentate N-heterocyclic ligands: From 3-D MOF to 1-D chain

Three copper coordination polymers [Cu-2(bbtc)(bbi)(2)]center dot 3H(2)O (1) [bbi - 1,1-(1,4-butanediyl)bis(imidazole), bbtc = 3,3',4,4'-benzophenonetetracarboxylate], [Cu-3(Hbbtc)(2)(3-bpfp)(3)(H2O)(2)]center dot 10H(2)O(2) [3-bpfp = bis(3-pyridylformyl)piperazine],and [Cu(H(2)bbtc)(4-bpfp)(H2O)]center dot H2O (3) [4-bpfp bis(4-pyridylformyl) piperazine] have been hydrothermally synthesized by self-assembly of aromatic tetracarboxylate ligand bbtcd [bbtcd 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride], and bidentate N-heterocyclic ligands bbi, 3-bpfp or 4-bpfp. X-ray diffraction analysis reveals that compound 1 is a novel three-dimensional (3-D) metal-organic framework with a binodal (4,4)-connected {6(2).8(4)}{6(4).8(2)} 2 topology. Compound 2 possesses a two-dimensional (2-D) layered structure, in which a trinodal (3,4,4)-connected network with novel {3.6(2)}(2){3.6(3).7(2)}(2){3(2).6(2).7(2)} topology can be found. Compound 3 displays a one-dimensional (1-D) ribbon polymer chain based on 4-bpfp ligands and H(2)bbtc(2-) anions. The adjacent layers for 2 and the adjacent chains for 3 are further linked by hydrogen bonding and pi-pi stacking interactions to form 3-D supramolecular networks. Importantly, bbtcd with different protonation extent displays three different coordination modes in compounds 1-3: the four carboxyl groups of bbtc(4-) anions combine with Cu-II ions by tetra(monodentate) mode in 1, three carboxyl groups of Hbbtc(3-) anions show tri(monodentate) coordination mode and the fourth carboxyl group is protonated in 2, whereas for 3 only two carboxyl groups H(2)bbtc(2-) anions adopt bis(monodentate) coordination mode and the other two are protonated. N-heterocyclic ligands play important roles in the construction of title complexes with different dimensionality. In addition, the electrochemical properties of the three copper compounds bulk-modified carbon paste electrodes have been reported. Crown Copyright (C) 2011 Published by Elsevier B. V. All rights reserved.