Syntheses, crystal structures, and photoluminescent properties of two new Cd(II) coordination polymers based on biphenyl-2,2′,4,4′-tetracarboxylate and dipyridyl-containing ligands

Two new Cd(II) coordination polymers, [Cd2(btc)(dpe)1.5(H2O)]n (1) and [Cd2(btc)(bpp)(H2O)]n (2), were prepared by the hydrothermal reaction of cadmium nitrate with H4btc (H4btc = biphenyl-2,2′,4,4′-tetracarboxylic acid) in the presence of 1,2-di(4-pyridyl)ethylene (dpe) and = 1,2-bis(4-pyridyl)propane (bpp), respectively, structurally characterized by single-crystal X-ray diffraction, and further characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. In 1, btc4− connect six Cd2+ ions, forming a 3-D (3,3,6)-connected [Cd2(btc)] net, and further connected by 1-D [Cd(dpe)]n chains to construct the final (4,5,6)-connected (42.52.65.7)(43.62.7)(45.53.64.72.8) net. In 2, a 3-D [Cd2(btc)] net is also constructed from btc4− connecting six Cd2+ ions, giving a 3-D (3,4,7)-connected network. The overall structure of 2 can be regarded as a (4,4,6)-connected (45.64) (42.5.62.8) (43.54.67.7) framework with bpp linking adjacent Cd ions. Structural comparisons show that the secondary auxiliary N-donors have important effects on the final structure and properties. Photoluminescent properties of 1 and 2 are also discussed.