New Metal–Organic Frameworks Constructed from the 4-Imidazole-Carboxylate Ligand: Structural Diversities, Luminescence, and Gas Adsorption Properties

Abstract

Reactions of metal ions with a rigid linear ligand 4-H2IBA incorporating 4-imidazolyl and carboxylate functional groups [4-H2IBA = 4-(1H-imidazol-4-yl)benzoic acid] under variable reaction conditions gave 11 new coordination polymers, [Cu(4-HIBA)2(H2O)4] (1), [CuIICuI(4-HIBA)(4-IBA)(H2O)2]·2.3H2O (2), [Cu(4-HIBA)(Cl)] (3), [Cu3(4-HIBA)6]·7.8H2O (4), [Cd(4-HIBA)2(H2O)]·2H2O (5), [Cd(4-HIBA)2] (6), [Cd(4-HIBA)2]·2DMF (7), [Cd2(4-HIBA)4]·H2O (8), [Zn(4-HIBA)2]·H2O (9), [Zn(4-HIBA)2]·C2H5OH·DMF (10), and [Co(4-HIBA)2]·2DMF (11). The copper complexes 1–4 are discrete molecules to three-dimensional (3D) infinite networks. Complexes 1 and 2 formed in different reaction temperatures exhibit a mononuclear motif and one-dimensional (1D) chain, respectively. Compounds 3 and 4 were obtained through controlling reaction solvent systems, and 3 features a two-dimensional (2D) (4,4) network by taking the binuclear [Cu2(Cl)2] as 4-connecting nodes, whereas 4 is a 3-fold interpenetrating mog net with Point (Schläfli) symbol of (4·64·8)2(42·62·82). The 4-HIBA– ligands act as rod-type two-connectors to connect metal Cd(II) centers into 4-connected 3D frameworks with different topologies: binodal 4-connected network with a Point (Schläfli) symbol of (86) (5) and uninodal (65·8) net (6), uninodal 4-connected [2 + 2] interpenetrating (66) dia net (7), and 5-fold interpenetrating dia net (8), respectively. Complex 9 has a 1D double chain structure, while 10 and 11 are isostructural as 7. Fluorescence and gas adsorption properties of the compounds have also been explored.