A series of new mixed ligand complexes of the ype [M(terpyridine H+) (amino acid)X2]-H20, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), X = Cl or NO3, have been synthesized and characterised by elemental analysis and infrared spectra. It is deduced that the coordination mode of the terpyridine is changed from terdentate in the binary complex to bidentate in the ternary one where the uncoordinated pyridine exists in the protonated form.

The mixed-ligand complexes are prepared by the reaction of thiobarbituric acid with five-coordinate Co(II), Ni(II) and Cu(II) of arylideneanthranilie acids. The so obtained complexes are characterised by elemental analyses, electronic and IR spectroscopy, X-ray powder diffraction patterns, and conductivity measurements. It is found that thiobarbituric acid coordinates as a neutral or mono-basic mono-dentate ligand to form carboxylate-bridged five-coordinate mixed-ligand complexes. Both the ligands and mixed-ligand complexes have been tested for their antimicrobial activities.

Four coordinate Ni(II) and Cu(II) chelates formed by reaction of two azopyrazolone derivatives with metal sulfate, acetate, or nitrate are described. It is concluded that the ligands possess tautomeric equilibria and can coordinate to the metal ion as neutral or monobasic bidentates. The so-obtained complexes are characterized by elemental and thermal analyses, IR and electronic spectra, as well as conductivity measurements. A pseudo-tetrahedral polymeric structure is proposed for all the complexes in which the acetate, nitrate, or sulfate is attached to the metal ion in the bridging bidentate mode. It is observed that the chelates formed are more potent as antimicrobial agents than the free ligands.