SYNTHESIS AND CHARACTERISATION OF 3-(CHLOROPHENYLHYDRAZO)-2,4-PENTANEDIONES AND THEIR METAL COMPLEXES WITH ENHANCED ANTIMICROBIAL ACTIVITY
A series of 3-(chlorophenylhydrazo)-2,4-pentanediones along with their Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) complexes were prepared and subsequently characterized through elemental composition, spectroscopic techniques (IR, UV–Vis, ¹H NMR, and mass), as well as magnetic and conductance measurements. Analytical results indicate an [ML3] stoichiometry for Cr(III) and Fe(III), while Mn(II) and Co(II) formcomplexesof the type [M(L)2(H2O)2], and Ni(II), Cu(II), and Zn(II) exhibit [ML2] composition. The ligands behave asmonobasic bidentate species, coordinating via the deprotonated hydrazone nitrogen and the carbonyl oxygeninvolved in hydrogen bonding. This coordination mode results in octahedral structures for Cr(III), Mn(II), Fe(III), and Co(II), square-planar arrangements for Ni(II) and Cu(II), and a tetrahedral geometry for Zn(II). Antimicrobial evaluation against Escherichia coli, Staphylococcus aureus, and Aspergillus niger revealed enhanced activity uponmetal coordination, with Mn(II), Ni(II), and Zn(II) complexes exhibiting the most significant effects. The observedvariation in activity across the metal series highlights the critical role of metal ion identity, coordination geometry, and chelate stability in governing biological performance. This study advances medicinal inorganic chemistrybyestablishing clear structure–activity relationships in chloro-substituted hydrazone complexes and demonstrates that rational selection of metal ions and ligand frameworks can effectively tune antimicrobial properties. These resultsoffer a basis for developing novel metal-containing antimicrobial agents aimed at tackling the increasing problemof antimicrobial resistance.
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