Schiff bases are versatile ligands, synthesized via condensation of primary amines with carbonyl compounds. In this study, equimolar amounts of 4-imidazolecarboxaldehyde and thiosemicarbazide were combined and the Schiff base 4-imidazolecarboxaldehyde thiosemicarbazone was prepared as a new bidentate complexing agent. The synthesized ligand was reacted with palladium (II) and platinum (II) ions yielding air-stable complexes. For characterization purpose, infrared spectra, mass spectra, electronic spectra, thermal analysis, proton nuclear magnetic resonance and 13-carbon nuclear magnetic resonance spectra studies were carried out on the obtained complexes and ligand. The characterization data showed that the ligand acts as a bidentate coordinate to the metal ions through azomethine nitrogen and sulfur atoms. An in vitro antimicrobial investigation was also carried out for the free ligand and its metal complexes against four bacteria; Bacillus cereus, Staphylococcus aureus (Gram-positive), Escherichia coli and Salmonella typhimurium (Gram-negative) and one Fungi; Candida albicans, to assess their antimicrobial properties by disc diffusion technique. Antimicrobial activity of the prepared complexes showed higher activity than the free ligand.

Das Acetylpyrolinon (I) läßt sich mit aromatischen Aldehyden zu den Cinnamoylpyrazolinonen (II), mit Formaldehyd und Aminen (HCl‐katalysiert in siedendem Ethanol) zu den Mannich‐Basen (III), mit Phenylhydrazin zum Pyrazolopyrazol (IV) umsetzen.

Schiff bases are regarded as “privileged ligands” due to their capability to form complexes with a wide range of transition metal ions yielding stable and intensely colored metal complexes. In this study, equimolar amounts of 4-methyl-5-imidazolecarboxaldehyde and thiosemicarbazide were combined and the Schiff base 4-methyl-5-imidazolecarboxaldehyde thiosemicarbazone was prepared as a new bidentate complexing agent. The synthesized ligand was reacted with palladium (II) and platinum (II) ions yielding air-stable complexes. For characterization purpose, mass spectra and x-ray analysis of the ligand and infrared spectra, electronic spectra, thermal analysis, proton nuclear magnetic resonance and 13-carbon nuclear magnetic resonance spectra studies were carried out on the obtained ligand and its complexes. The characterization data showed that the ligand acts as a bidentate coordinate to the metal ions through azomethine nitrogen and sulfur atom. An in vitro antimicrobial investigation was also carried out for the free ligand and its metal complexes against four bacteria; Bacillus cereus, Staphylococcus aureus (Gram-positive), Escherichia coli and Salmonella typhimurium (Gram-negative) and one Fungi; Candida albicans. The results showed that the antimicrobial activity of the prepared complexes showed higher activity than the free ligand.

The New ligand 5-methyl-2-(2-thienyl)-1,3-oxazole-4-carbaldehyde thiosemicarbazone (HL)(1) was synthesized. This ligand reacted with Co(II) and Ni(II) chloride in ratio 1:2 metal:ligand afforded two complexes, [Co(LH)]Cl2 (2) and [Ni(HL)2]Cl2 (3). The ligand and its metal (II) complexes have been characterized by spectroscopic techniques. The X-ray structural studies revealed that the free ligand exist in thione form and remain as neutral tridentate with NNS donor atoms in the tow complexes beside presence of uncoordinated chloride ions in the cavities of the crystal lattice of the complexes. One of these chlorides in complex (2) is hydrogen bonded to a proton of the amine of the ligand. While in complex (3) the chloride bonded to proton of imine (-N2H) of the ligand and the coordination environment has a distorted octahedral. The oxazole N and S atoms in the two complexes are cis to each other whereas the azomethine N atoms are trans coordinated. The ligand and its metal complexes were tested for their in vitro biological activity against six standard microorganisms: two Gram positive namely Bacillus subtilis and Micrococcus luteus, and one Gram negative bacteria Escherichia coli and three fungi: Saccharomyces cerevisiae (Baker’s yeast), Mucor spec., and Aspergillus niger, at a concentration 100µg/ml.