Synthesis, spectroscopic, thermal, DNA binding, antibacterial, antifungal and molecular docking studies: Antipyrine hydrazone ligand and its transition metal complexes

Cu(II), Co(II), Ni(II), Mn(II) and UO2(II) complexes of 1,5-dimethyl-4-(2-methyl-5-oxo-1-phenyl-1H-pyrazol-4 (5H)-ylidene)hydrazainyl)-2-phenyl-1,2-dihydropyrazol-3-one (HL) ligand have been synthesized and characterized by different analytical techniques. FT-IR spectra demonstrated that the ligand under investigation behaves as a di/tridentated center ligand (NO/ONO) through the nitrogen/NH atom of the hydrazon group which is the farthest of the antipyrine moiety and oxygen carbonyl pyrazole/carbonyl antipyrine for heterocyclic moiety and forms a stable six/five-membered chelating ring. The results revealed a tetrahedral geometry for complexes (1 & 4) and an octahedral geometry for complexes (2, 3 & 5). The agar well diffusion method, serial dilution method (MIC), and minimum microbicidal concentration (MMC) were tested to study the antimicrobial activities of start, ligand, and complexes compared to penicillin G and miconazole as standards. The obtained results revealed that complexes are more effective than start and free ligand. The coordination sites of nitrogen atoms of the hydrazon group and oxygen of the carbonyl group as well as the high lipophilicity of the complexes might be the main factors for their good inhibitory action against the tested bacterial and fungal strains. The Ni(II) and Mn (II) complexes were found to be the most potent compounds with inhibition zones ranging from 16 to 27 mm, MIC and MMC values of 5-25 mu g/mL, Mn(II) complex was most active against all bacterial strains, whereas Cu (II), Ni(II), Co(II) and UO2(II) complexes were most efficient for the fungal strains with inhibition zones ranged from 8 to 19 mm, MIC and MMC values of 45-50 mu g/mL.