Metal–organic coordination architectures with 3-pyridin-3-yl-benzoate: crystal structures, fluorescent emission and magnetic properties

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Reactions of 3-pyridin-3-yl-benzoic acid (HL) with metal nitrates under hydrothermal conditions yield seven new coordination polymers: Ni(L)2(H2O)2 (1), [Ni(L)2](H2O) (2), Co(L)2(H2O)2 (3), [Zn(L)2](H2O) (4), Cu(L)2 (5), Cd(L)2 (6) and Gd2(L)6(H2O)4 (7). A systematic investigation on coordination chemistry of the ligand and the significant function of supramolecular interactions in managing the resultant crystalline networks has been carried out. On the basis of the X-ray diffraction analysis of these complexes, the results show that complexes 1–5 and 7 form similar one-dimensional (1D) double-chain coordination arrays, among which 1 and 3, as well as 2 and 4, are isostructural. Remarkably, distinct network architectures are further constructed with the aid of weak secondary interactions. Amongst them, complexes 1, 3 and 5 exhibit the classical α-polonium networks, while complexes 2 and 4 present the (3,4)-connected two-dimensional layers. In 7, the intermolecular π–π stacking interactions lead to the formation of a double-strand structure. The CdII complex 6 assembles into a three-dimensional metal–organic framework exhibiting a unique 6-connected roa topology. The trans-configuration of L ligand is only found in the case of 6, whereas the cis-ligands are generally observed in these complexes. The fluorescent emission properties of 4 and 6 as well as the magnetic property of 7 have also been investigated.