Syntheses and characterization of two novel cadmium(II) coordination polymers derived from pyridyl substituted terpyridine and diphenate mixed ligands

Two metal-organic coordination polymers, [Cd(dpa)(pytpy)]·(H2O)3 (1) and [Cd3(dpa)(pytpy)2(SO4)2]·(H2O)3 (2), have been synthesized by the reactions of 4′-(3-pyridyl)-2,2′:6′,2′′-terpyridine (pytpy), diphenic acid (H2dpa) with Cd(ClO4)2·6H2O and CdSO4·8/3H2O, respectively, in the presence of base. Compound 1 is a one-dimensional helical chain, in which (dpa)2− as bridging ligand is responsible for the formation of the main framework and pytpy as chelating ligand grafts on one side of the helical chain and forms π-π stacking interactions with adjacent chains. This compound is further extended into a two-dimensional supramolecular framework through hydrogen bonds. Compound 2 is a one-dimensional chain simultaneously composed of bridging neutral organic ligand, bridging anionic organic ligand and bridging anionic inorganic ligand. The (dpa)2− and sulfate anions connect CdII atoms into neutral [Cd3(dpa)(SO4)2] subunits and the trinuclear units are bridged by pytpy ligand into one-dimensional double-layer chain. This structure is further extended into two-dimensional layer architecture through face-to-face π-π interactions.