Mn(II) and Zn(II) ions catalytic oxidation of o-phenylenediamine and characterization, X-ray crystal structure and solution study of the final products DAPH+Cl−·3H2O and [DAPH][Zn(dipicH)(dipic)]·4H2O

Compound DAPH+Cl−·3H2O (1), and complexes Mn(dipic)(H2O)3 (2) and [DAPH][Zn(dipicH)(dipic)]·4H2O (3), (dipicH2 = 2,6-pyridinedicarboxylic acid and DAP = 2,3-diaminophenazine) were prepared from the reaction of MgCl2·4H2O and ZnCl2 with mixture of o-phenylenediamine (OPD) and 2,6-pyridinedicarboxylic acid in water. These compounds were characterized by elemental analysis, FTIR, 1H NMR and UV–Vis spectroscopy. The solid-state structure of [DAPH][Zn(dipicH)(dipic)]·4H2O (monoclinic, P21/c) was determined by the single crystal X-ray diffraction method. The protonation constants of dipic and DAP, in all of probability protonated forms, the equilibrium constants for the dipic–DAP proton transfer system and the stoichiometry and stability constants of binary and ternary complexes of this system with Zn2+ and Mn2+ ions in aqueous solution were investigated by the potentiometric pH titration method. The stoichiometries of the most complex species in solution were compared with corresponding crystalline complexes in the solid state.We gratefully acknowledge the support of this work by the Sistan and Baluchestan University. Financial support from Spanish Ministerio de Economia y Competitividad (MAT2013-40950-R) and ERDF funding is acknowledged.Peer Reviewe