Syntheses, structures and photoluminescent properties of a series of divalent nickel and cadmium complexes based on 3-carboxy-1-(4′-(2″-carboxy)biphenylmethyl)-2-oxidopyridinium and structurally different N-donor ligands

Abstract

Ten new coordination polymers, namely, [Cd(L)(pbib)0.5] (1), [Ni(L)(pbib)]·2H2O (2), [Cd2(L)2(pytp)2]·H2O (3), [Cd(L)(tbpy)] (4), [Ni(L)(pytp)] (5), [Ni(L)(tbpy)]·0.25H2O (6), [Cd(L)(biim-6)0.5] (7), [Cd(L)(phen)] (8), [Cd3(L)3(H2O)]·H2O (9), and [Cd3(L)3(biim-4)0.5]·6H2O (10), where biim-4=1,1′-(1,4-butanediyl)bis(imidazole), biim-6=1,1′-(1,6-hexanedidyl)bis(imidazole), pbib=1,4-bis(imidazol-1-ylmethyl)benzene, phen=1,10-phenanthroline, pytp=2-(6′-(pyridin-2″-yl)-4′-p-tolylpyridin-2′-yl)pyridine, tbpy=2-(4′-(4″-tert-butylphenyl)-6′-(pyridin-2″-yl)pyridin-2′-yl)pyridine and H2L=3-carboxy-1-(4′-(2″-carboxy)biphenylmethyl)-2-oxidopyridinium, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Compounds 1 and 2 show layer structures. Neighboring layers are further linked by π–π stacking interactions to form 3D supramolecular architectures. Compound 3 consists of two crystallographically different dimers, which are further linked by π–π and hydrogen-bonding interactions into a 2D supramolecular architecture. Compounds 4–6 feature chain structures. In 4, neighboring chains are stacked by π–π interactions to result in a 2D supramolecular architecture. In 5, the adjacent chains are linked by π–π interactions to yield a 3D supramolecular architecture. In 6, neighboring chains are further linked by hydrogen-bonding interactions into a 3D supramolecular architecture. Compound 7 exhibits a 2D 63-hcb network. Neighboring networks are further extended by π–π stacking interactions into a 3D supramolecular architecture. Compound 8 displays a (4,4) sheet. Compound 9 reveals a 2D (4,4) network. Compound 10 shows a 3D 5-connected framework with (46·64) topology. The effects of the L anions and the N-donor ligands on the structures of the coordination polymers have been discussed. In addition, the luminescent properties of 1, 3, 4 and 7–10 have also been investigated in details.