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.