A new neodymium(III)-calcium(II) one-dimensional coordination polymer constructed from dipicolinic acid: synthesis, crystal structure, spectroscopic and thermal analysis, and solution studies

A new heterometallic supramolecular coordination polymer, namely [(1-mimH)[Nd(pydc)(3)Ca(pydcH(2))(H2O)(2)]center dot 4H(2)O] (n) (where pydcH(2) = pyridine-2,6-dicarboxylic acid (dipicolinic acid), 1-mim = 1-methylimidazole) has been prepared and characterized by elemental analysis, spectral (IR, UV-Vis), H-1 NMR and C-13 NMR spectroscopy, thermal analysis as well as single-crystal X-ray diffraction. The X-ray diffraction study demonstrates that the compound has a 1D network; the layers of this compound are connected by complicated hydrogen bonds to form 3D supramolecular architecture. The polymeric chain contains Nd(III) ions and Ca(II) ions bridged by (pydc)(2-) ligands. Each (pydc)(2-) ion is connected to one neodymium(III) ion as a tridentate ligand and one calcium ion via bridging carboxylate group. The equilibrium constants of dipicolinic acid and 1-methylimidazole, pydc/1-mim proton transfer system, as well as those of the complexes (binary, ternary, and quaternary) were investigated by potentiometric pH titration method. .