Construction of metal-organic frameworks with the pyridine-3,5- dicarboxylate anion and bis(imidazole) ligands: Synthesis, structure, and thermostability studies

摘要

Three novel metal-organic polymers, namely, [Ni(L~1) _(0.5)(3,5-pdc)(μ-H_2O)]·H_2O (1), [Co(L~2)(3,5-pdc)]·2H_2O (2), and [Co(L ~3)(3,5-pdc)(μ-H_2O)]·H_2O (3) [3,5-pdc = pyridine-3,5-dicarboxylate, L~1 = 1,4-bis(imidazol-1-ylmethyl) benzene, L~2 = 1,1'-(1,4-butanediyl)bis(imidazole), and L~3 = 1,1'-(1,4-hexanediyl)bis(imidazole)], have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction (XRD), thermogravimetric (TG) analysis, and elemental analysis (EA). Polymers 1 and 2 have the identical 2D [M(3,5-pdc)] sheet skeleton, however, different bis(imidazole) ligands cause 1 to have a 2D (3,4)-connected double-layer net featuring the (6 ~3)(6~4·8~2) topology symbol and 2 to have a 2D (3,5)-connected net characterized by the (3 5~2)(3 ~2·5~3·6~4·7) topology symbol. They are both extended to 3D supramolecular frameworks through the O-H···O hydrogen bonds. In particular, in 2 there exists a four-membered Z-shape water cluster. The Co ions in 3 are connected by 3,5-pdc and L~3 to give rise to a complicated 3D framework that can be described as a (3,5)-connected (4~2·5)(4~2· 6~3·8~2·10~2·12) network. In addition, the thermal analysis of these three complexes has been measured and discussed. Three complexes, which self-assembled from the metal ions, pyridine-3,5-dicarboxylic acid, and the bis(imidazole) ligands, show desirable structural features that depend on both the coordination modes of the 3,5-pdc~2- anions and the various configurations of the N-donor ligands.