Three Novel Cd(II) Metal−Organic Frameworks Constructed from Mixed Ligands of Dipyrido[3,2-<i>d</i>:2‘,3‘-<i>f</i>]quinoxaline and Benzene-dicarboxylate: From a 1-D Ribbon, 2-D Layered Network, to a 3-D Architecture

Abstract

The use of dipyrido[3,2-d:2‘,3‘-f]quinoxaline (Dpq) combined with three structurally related benzene-dicarboxylic acid ligands [benzene-1,3-dicarboxylic acid (H2L1), benzene-1,2-dicarboxylic acid (H2L2), and biphenyl-4,4‘-dicarboxylic acid (H2L3)] has allowed the rational design of three novel Cd(II) coordination polymers, [Cd3(Dpq)3(L1)3]·4.5H2O (1), [Cd(Dpq)(L2)(H2O)] (2), and [Cd2(Dpq)2(L3)2]·1.5H2O (3), which were hydrothermally synthesized and structurally determined by X-ray analysis. Compound 1 features a 1-D ribbonlike structure, compound 2 shows novel 2-D four-connected networks, and compound 3 possesses an interesting 6-connected 2-fold interpenetrated 3-D α-Po-related architecture. The Dpq ligand takes a chelating coordination mode while the other two nitrogen atoms did not coordinate to the Cd(II) ions. In these complexes, the three benzene−dicarboxylate ligands are able to link Cd(II) ions in various coordination modes, giving rise to 1-, 2-, and 3-dimensional Cd complexes, respectively. In addition, complexes 1−3 exhibit blue/green emission in the solid state at room temperature.