Synthesis, crystal structure, spectroscopic and electrochemical properties of nickel(II) dipicolinate complex with ethylisonicotinate

Abstract

The diaqua(ethylisonicotinate)(pyridine-2,6-dicarboxylato)nickel(II) monohydrate complex was synthesized and characterized by spectroscopic (IR, UV/vis), X-ray diffraction and electrochemical methods. The Ni(II) ion is bonded to dipicolinate (dpc) through pyridine N atom and one O atom of each carboxylate group, two aqua ligands and N pyridine atom of ethylisonicotinate (ein), form the distorted octahedral geometry. The molecules are connected via O-H O hydrogen bonds, forming R-4(4)(12) motifs in three dimensional networks. IR and UV-Vis spectroscopies agree with the observed crystal structure. The voltammetric behaviour of the complex was investigated in aqueous solution by square-wave and cyclic voltammetry using a NH3/NH4Cl buffer. The square-wave voltammogram of the complex yields three reduction peaks at -0.88, -1.20 and -1.28 V. The irreversible reduction as a shoulder at -1.20 V is due to Ni-dpc-ein complex. The peak at -0.88 V corresponds to irreversible electrode process of Ni(II)-ein complex while the peak at -1.28 V is attributed to the reduction of the coordinated dpc ligands.