A proton transfer and a cobalt(II) compound including 2,6-pyridinedicarboxylate and o-phenylenediamine ions: Synthesis, characterization, crystal structure and solution study

A proton transfer compound, (OPDH)2(dipic), (dipicH2 = 2,6-pyridinedicarboxylic acid and OPD = o-phenylenediamine), was synthesized and characterized by IR, 1H and 13C NMR spectroscopy. The reaction of (OPDH)2(dipic) with CoCl2·6H2O in water results in the formation of the novel complex [OPDH]2[Co(dipic)2]·H2O (1). This complex was characterized by elemental analysis, UV–vis, FTIR and the single-crystal X-ray methods. The crystal system is triclinic with space group P1. The protonation constants of dipic and OPD, the equilibrium constants for the dipic-OPD proton transfer system, the stoichiometry and the stability of complexation of this system with the CoII ion in an aqueous solution were investigated by the potentiometric pH titration method using Hyperquad 2008 program. The stoichiometry of the complex species in solution was the same as that of the metal ion complex found in the solid state.