Structures and Photoluminescence Properties of Four Cadmium(ii) Coordination Polymers Synthesized by Rigid Ligands and N-Donor Ligands

Four metal-organic coordination polymers, [Cd-2(dna)(2)(2,2-bpy)(2)](n) (1), {[Cd-4(dna)(4)(im)(3)]5H(2)O}(n) (2), {[Cd-2(dna)(2)(4,4-bpy)(H2O)(2)]2EtOH}(n) (3), and {[Cd-4(dna)(4)(1,3-dpp)(4)(H2O)(4)]2H(2)O}(n) (4) (H(2)dna=4,6-dimethyl-5-nitroisophthalic acid; 2,2-bpy=2,2-bipyridine; im=imidazole; 4,4-bpy=4,4-bipyridine; 1,3-dpp=1,3-di(4-pyridyl)propane; and EtOH=ethanol, have been solvothermally synthesized and characterized. Compound 1 displays a one-dimensional (1D) ladder structure and the neighbouring ladders are further stabilized by interactions to form a two-dimensional (2D) layer. Compound 2 forms a 2D layer based on infinite 1D [Cd-2(COO)(4)](n) chain and the im ligands act as terminal ligands, preventing expansion of the dimensionality. Compound 3 features a 2D 4(4)-sql layer based on binuclear [Cd-2(COO)(4)] secondary building units as 4-connected nodes, and is further linked to be an unusual three-dimensional (3D) supramolecular architecture by hydrogen bonds involving the coordinated water molecules, carboxylate groups, and lattice ethanol molecules. Compound 4 possesses a 2-fold interpenetrated dia net. The diverse structures and topologies of compounds 1-4 indicate that the N-containing ligands have significant effects on the formation of the final network structures. In addition, the thermal stabilities, structure comparison, and photoluminescence properties of the complexes have been investigated.