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-H 2 IBA incorporating 4-imidazolyl and carboxylate functional groups [4-H 2 IBA = 4-(1 H -imidazol-4-yl)benzoic acid] under variable reaction conditions gave 11 new coordination polymers, [Cu(4-HIBA) 2 (H 2 O) 4 ] ( 1 ), [Cu II Cu I (4-HIBA)(4-IBA)(H 2 O) 2 ]·2.3H 2 O ( 2 ), [Cu(4-HIBA)(Cl)] ( 3 ), [Cu 3 (4-HIBA) 6 ]·7.8H 2 O ( 4 ), [Cd(4-HIBA) 2 (H 2 O)]·2H 2 O ( 5 ), [Cd(4-HIBA) 2 ] ( 6 ), [Cd(4-HIBA) 2 ]·2DMF ( 7 ), [Cd 2 (4-HIBA) 4 ]·H 2 O ( 8 ), [Zn(4-HIBA) 2 ]·H 2 O ( 9 ), [Zn(4-HIBA) 2 ]·C 2 H 5 OH·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 [Cu 2 (Cl) 2 ] as 4-connecting nodes, whereas 4 is a 3-fold interpenetrating mog net with Point (Schläfli) symbol of (4·6 4 ·8) 2 (4 2 ·6 2 ·8 2 ). 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 (8 6 ) ( 5 ) and uninodal (6 5 ·8) net ( 6 ), uninodal 4-connected [2 + 2] interpenetrating (6 6 ) 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.