Syntheses, crystal, and molecular structures of Mn(II), Zn(II), and Ce(III) compounds and solution studies of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Ce(III) compounds obtained from a suitable proton transfer compound containing bda and pydcH_2 (bda = butane-1,4-diamine; pydcH_2 = pyridine-2,6-dicarboxylic acid)

摘要

Three new metal-organic compounds formulated as (H_2bda)[Mn(pydc)_2]·3H_2O (1), (H_2bda)[Zn(pydc)_2]·3H_2O (2), and (H_2bda)_3[Ce(pydc)_3]_2·4H_2O (3) have been synthesized and structurally characterized by elemental analyses, IR, ~1H and ~(13)C NMR spectroscopies, and single crystal X-ray diffraction method. The asymmetric units of 1 and 2 contain three water molecules where in both compounds the corresponding metallic center is six-coordinated by two N and four O atoms as a distorted octahedral. The asymmetric unit of 3 contains four water molecules and the Ce(III) atom is nine-coordinated by three N and six O atoms in a distorted tricapped trigonal prism that the N atoms capping the faces. In the crystalline network of these three coordination compounds, hydrogen bonds, π-π stacking, and ion pairing play basic roles in the formation of supramolecular structures, in which they seem to be effective factor in the stabilization of the structure. The protonation constants of bda and pydcH_2 and the (H_2bda)(pydc) proton transfer equilibrium constants, the stoichiometry and stability of complexes of above mentioned ion pair with Mn~(2+), Ni~(2+), Cu~(2+), Zn~(2+), Cd~(2+), and Ce~(3+) metal ions in aqueous solution were investigated by potentiometric pH titration method. The stoichiometry of the most complexed species in solution was compared with corresponding crystalline complexes in the solid state.