Synthesis, Structural, Spectroscopic, Thermal and Voltammetric Properties of 5,5-Diethylbarbiturato Complexes of Zinc with 2-(2-Aminoethyl)pyridine and 2-(2-Hydroxyethyl)pyridine

Abstract

Two new bis(5,5-diethylbarbiturato) (barb) complexes of zinc, [Zn(barb)<inf>2</inf>(aepy)] (1), [Zn(barb)<inf>2</inf>(hepy)] (2) [aepy = 2-(2-aminoethyl)pyridine and hepy = 2-(2-hydroxyethyl)pyridine], have been prepared and characterized by elemental analysis, FT-IR spectroscopy, thermal analysis and single crystal X-ray diffraction. Complex 1 crystallizes in the triclinic P1 space group; crystals of complex 2 could not be obtained. The zinc(II) in complex 1 is tetrahedrally coordinated by two barb and an aepy ligand. The barb ligands are N-coordinated while the en ligand acts as a bidentate N,N′ chelate. One of the carbonyl oxygen atoms of each barb ligand makes a remarkably long bond to zinc and in this case, coordination geometry can be considered as a highly distorted octahedron. The molecules of complex 1 are connected via N-H ⋯ O hydrogen bonds, involving hydrogen atoms of both barb and aepy ligands. The voltammetric behavior of complexes 1 and 2 was investigated in aqueous solution by cyclic voltammetry using a NH <inf>3</inf>/NH<inf>4</inf>Cl buffer. The cyclic voltammograms of both complexes are similar, showing well-defined cathodic and anodic peaks at -1.29 and -1.10 V, respectively, due to a quasi-reversible two-electron transfer of the complexed zinc(II) ions. © 2007 Taylor & Francis.