pH-controlled synthesis of two new coordination polymers modeled by pyridine-2,4-dicarboxylic acid

Two new cadmium compounds [Cd3 (OH)2 (2,4-pydc)2] (1) and [Cd2(2,4-pydc)2(bpe)]·2H2O (2) (2,4-pydcH2 = pyridine-2,4-dicarboxylic acid, bpe = 1,2-bis(4-pyridyl)ethene) have been prepared under hydrothermal conditions at different pH values. The compounds were characterized by elemental analyses, IR spectra and thermogravimetric analyses and their structures were determined by single-crystal X-ray diffraction analysis. Compound 1 has a 3D framework constructed by 2D Cd-O(OH) layers and pillared 2,4-pydc ligands. Compound 2 also displays a 3D metal-organic framework with the Cd(II) centers connected by 2,4-pydc and bpe ligands. The differences in the structures indicate that the change of pH value has significant effects on the formation and structures of the final compounds. In addition, the luminescent properties of compounds 1–2 have also been studied.