Five d10 3D metal-organic frameworks constructed from aromatic polycarboxylate acids and flexible imidazole-based ligands

Five new metal-organic frameworks, namely, [Cd(HIDC)(bix)](n) (1), [Cd-2(BDC)(2)(mbix)H2O](n) (2), [Cd(HBTEC)-(H(2)bix)0.5](n) (3), [Cd(BTEC)(H(2)mbix](n) (4), and [Zn(BTEC)0.5(mbix)](n) (5) (H3IDC = imidazole 4,5-dicarboxylic acid, H2BDC = 1,4-benzenedicarboxylate, H4BTEC = 1,2,4,5 -benzenetetracarboxylate, bix = 1,4-bis(imidazol-1-ylmethyl)-benzene, and mbix = 1,3-bis(imidazol-1-ylmethyl)-benzene), have been synthesized under hydrothermal conditions by employing mixed ligands of various carboxylic acids with bix (or mbix). Coordination polymer I is a 3 - fold- interpenetrated diamondoid network. Particularly, in 1 there occur triple-stranded helices based on Cd ions and bix ligands when viewed along b axis. Coordination polymer 2 is a 2D infinite layer framework, which is further interconnected by hydrogen-bond interactions leading to a 3D supramolecular architecture. Both 3 and 4 feature a 3D open framework with protonated bix (or mbix) locating in the channels, and the 3D open frameworks can be rationalized as a zeolite ABW topology for 3 and pts net for 4. Coordination polymer 5 also has a 3D architecture, and the topological study shows that its framework features a 3D four-connected (6(4)8(2))(6(6)) net. The photoluminescent properties of the coordination polymers were investigated. All of these coordination polymers exhibited intense fluorescent emissions in the solid state at room temperature.