Novel Proton Transfer Compounds Containing 2,6-Pyridinedicarboxylic Acid and Melamine and Their Pb~(II) Complex: Synthesis,Characterization,Crystal Structure and Solution Studies

摘要

Two novel proton transfer compounds LH_2,(tataH_2)(pydc),and L'H_2,(tataH)_2(pydc),(pydcH_2 = 2,6-pyridinedicarboxylic acid and tata = melamine,2,4,6-triamino-1,3,5-triazine),were synthesized and characterized by IR,~1H and ~(13)C NMR spectroscopy and solid state CPMAS ~(13)C NMR.The (tataH_2)_2[Pb(pydc)_2]_2 centre dot 2tata centre dot 4H_2O complex (1) was prepared using L'H_2 and lead(II) nitrate,and characterized by IR and NMR spectroscopy and single crystal X-ray analysis.The Pb complex is a binuclear anionic complex [Pb(pydc)_2]_2~(4-),which two metal fragments are linked via a central ten-membered PbN(13)C(18)C(22)O(24)Pb(A)N(13A)C(18A)C(22A)O(24A) ring.Extensive hydrogen bonding between carboxylate groups,(tataH_2)~(2+) and water molecules throughout the Pb~(II) complex together with ion pairing play important roles in stabilizing the corresponding lattice.The protonation constants of the reactants,the equilibrium constants for the reaction of pydc with tata and the stoichiometry and stability of the Pb~(II) complex with L'H_2 in aqueous solution were investigated by potentiometric pH titrations.The stoichiometry of one of the most abundant complexed species in solution was found to be the same as that of the crystalline lead complex.