ABSTRACT

Two novel acylpyrazolone ligands; (1-(5- hydroxy-3-methyl-1-phenyl-1-H-pyrazol-4-yl) pentan-1-one (HMPPp) and 1-(5-hydroxy-3-methyl-1-phenyl-1-H-pyrazol-4-yl) nonadecan-1-one (HMPPn) were synthesized by reacting pentanoyl chloride with 3-methyl-1-phenylpyrazol-5-one and nonadecanoyl chloride with 3-methyl-1-phenylpyrazol-5-one respectively. Fe(III), Mn(II), and Ti(III) metal complexes of both ligands were also synthesized. The ligands and complexes were characterized based on elemental analysis, IR, 1HNMR and 13CNMR spectroscopy. Physical properties such as colour, melting points and solubility profile were also determined for both the ligands and the complexes. The ligandscomplexed through its C=O and deprotonated hydroxyl group. The CO-M and O-M bond stretching frequencies of the metal complexes were compared with that of the ligand. The result showed that, increase in electron density; caused the bond length to increase and consequently the vibrational frequencies were shifted upfield. The ligand and its metal complexes studied are not ionic in nature. The solubility data showed that the complexes are soluble in organic solvents. Furthermore the result on the antimicrobial of the ligand as well as the metal complexes against three gram positive bacteria (Staphylococcus aureus, Bacillus subtillsand Streptococcus aureus), three gram negative bacteria (Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa), and  threefungals  which include Aspergilusniger, candida albicansandSacharomycescerevisiae showed  that they are biologically active and there activity has been attributed to the presence of anazomethane and hydroxyl group in the pyrazolone ring. The study on the minimum inhibitory concentration (MIC) of both ligands (HMPPp and HMPPn) and their complexes showed that there were growths of inhibition in all the microbes inoculated at 0.1 and 0.025 μg/ml.From the studies, it was observed that the metal ions under investigation can be sequestrated using these ligands. However, the zones of inhibition of the complexes were observed to be remarkably higher than those of the ligands. The result on the solvent extraction showed that pH level values of 3 – 4.5 favoured the extraction of the metal by the ligands, and remained valid up to pH levels of 4.5. Also the average logarithms of the equilibrium constant (Kex) values for the metals at the different extractant concentrations at a constant pH of 4 showed that the ligands are more efficient in the recovery of Mn(II) > Fe(III) > Ti(III) from their aqueous solutions.