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.