1D, 2D, and 3D Metal−Organic Frameworks Based on Bis(imidazole) Ligands and Polycarboxylates: Syntheses, Structures, and Photoluminescent Properties

Abstract

Ten new coordination polymers constructed from two structurally related ligands, 1,1′-(1,5-pentanedidyl)bis(imidazole) (biim-5) and 2,2′-bis(1H-imidazolyl)ether (BIE), have been synthesized: [Co(L1)(biim-5)] (<b>1</b>), [Co(L2)(biim-5)]·H₂O (<b>2</b>), [Co(L3)(biim-5)] (<b>3</b>), [Co(L4)(biim-5)]·4H₂O (<b>4</b>), [Co(L5)_0.5(biim-5)] (<b>5</b>), [Co₂(L6)(BIE)₂]·1.5H₂O (<b>6</b>), [Zn₂(L6)(BIE)₂]·2.5H₂O (<b>7</b>), [Cd(L6)_0.5(BIE)(H₂O)]·H₂O (<b>8</b>), [Zn₂(L7)(BIE)₂]·H₂O (<b>9</b>) and [Cd(L8)_0.5(BIE)(H₂O)] (<b>10</b>), where H₂L1 = 1,2-benzenedicarboxylic acid, H₂L2 = 1,3-benzenedicarboxylic acid, H₂L3 = 5-OH-1,3-benzenedicarboxylic acid, H₂L4 = DL-camphoric acid, H₄L5 = 1,2,3,4-butanetetracarboxylic acid, H₄L6 = 4,4′-oxidiphthalic acid, H₄L7 = 4,4′-(hexafluoroisopropylidene)diphthalic acid, and H₄L8 = 1,2,3,4-benzenetetracarboxylic acid. Compounds <b>1</b> and <b>4</b> display the same 2D layer structures with 6³-<b>hcb</b> nets, but in <b>4</b> the water tetramers extend the layers to a 3D supramolecular framework by intermolecular hydrogen bonds. Compound <b>2</b> is an uncommon example of 2D double layers with the Schläfli symbol of (4²·6³·8). <b>3</b> shows a 2D <b>sql</b> net with large open windows, while <b>5</b> exhibits a rare 3,4-connected (8³)₂(8⁵·10) topology. The crystal structures of <b>6</b> and <b>7</b> are close to being isostructural with a scarce (3²·6²·7²)(3²·4·6²·7)₂ topology. <b>8</b> contains two kinds of chiral layers, one left-handed and the other right-handed, with a unique topological type of (5²·6⁴)(5³·6²·7)₂. Compound <b>9</b>, related by a pseudocenter of inversion, possesses a 3D porous framework with a (3,4)-connected (4·10²)₂(4²·10⁴)-<b>dmd</b>-net. <b>10</b> shows a 1D chain structure. The structural and topological differences of these ten compounds indicate that the polycarboxylate ligands play important roles in producing novel frameworks and topologies of the coordination complexes. The infrared spectra and thermogravimetric and luminescent properties were also investigated for the compounds.