Hydrothermal syntheses of a series of novel cis- and trans-pydc complexes with three-dimensional supramolecular architectures (pydc=pyridine-2,5-dicarboxylic acid)

Reaction of Fe(II) salts and Cd(II) salts with pyridine-2,5-dicarboxylic acid (H2pydc) under different hydrothermal temperatures give rise to four novel complexes: trans-[Fe(Hpydc)2(H2O)2] (1), cis-[Fe(Hpydc)2(H2O)2] (2), trans-[Cd(Hpydc)2(H2O)2] (3) and cis-[Cd(Hpydc)2(H2O)2] (4). They have been characterized by elemental analyses, infrared spectra (IR), UV-vis spectra, magnetic measurements and X-ray single crystal diffraction. In the complexes, the central Fe(II) ions or Cd(II) ions are coordinated by two water molecules and two chelated Hpydc ligands, and the intermolecular hydrogen bonds play an important role on the additional stabilization to construct the supramolecular networks in the packing structures. The water molecules coordinate with Fe(II) ions or Cd(II) ions in a trans mode in complex 1 and 3 while the water molecules coordinate in a cis mode in complex 2 and 4.