Novel CuII, CoII and PbII supramolecular networks of pyridine-2,6-dicarboxylate (pydc) in cooperation with a bent dipyridyl spacer via coordinative, hydrogen-bonding and aromatic stacking interactions

Reaction of M(OAc)(2) (M-II = Cu-II for 1, Co-II for 2, and Pb-II for 3) with pyridine-2,6-dicarboxylic acid (H(2)pydc) in presence of a dipyridyl spacer 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) affords three novel metal-organic supramolecular networks [Cu-2(bpo)(pydc)(2)(H2O)(3)] (.) 2.75H(2)O(1), [Co(bpo)(pydc)(H2O)(2)] (.) (H2O) (2) and [Pb(pydc)](n) (3), which have been structurally determined by single-crystal X-ray diffraction. The dimeric Cu-pydc coordination framework bridged by a bpo spacer in 1 is hydrogen-bonded to four others to result in a two-dimensional (2-D) sheet array. The neutral monomeric molecules in 2 have an ordered 3-D stacking stabilized via hydrogen bonds and significant pi-pi interactions in the lattice, possessing large porous channels with the inclusion of guest solvates. In coordination polymer 3, the Pb-II ion takes the unusual distorted capped trigonal prismatic geometry (PbNO6) and each pydc dianion binds to four Pb-II centres to form a 2-D infinite network. The thermal stabilities of these complexes have also been investigated. (c) 2005 Elsevier B.V. All rights reserved.