Metal complexes of hydrazone–oxime derivative as promising in vitro antimicrobial agents against some fungal and bacterial strains

Abstract

In this study, Cu2+, Co2+, Ni2+, Mn2+, Zn2+, Fe3+, VO2+, and UO22+ complexes derived from a NNO tridentate chelating hydrazone–oxime, namely, N′‐((2E,3Z)‐3‐(hydroxyimino)butan‐2‐ylidene)benzohydrazide (H2L,1) were prepared. The elemental, thermo‐gravimetric, spectral, molar conductivity, and magnetic measurements were applied to elucidate the compositions and structures of these new compounds. In addition to the density functional theory (DFT), studies were employed to acquire optimal structures and quantum chemical parameters. The analyses indicate that the chelator reacted as a neutral or mononegative tridentate ligand bonded to the metal ions via the enolic/ketonic carbonylic oxygen, protonated/deprotonated oximatic nitrogen, and azomethine nitrogen atoms adopting square planar or distorted octahedral geometry. The structural characterization of hydrazone–oxime and its complexes was supported by DFT calculations according to the DFT‐B3LYP procedure and 6‐311+G(d,p) basis set. The theoretical data revealed that the reactivity of the complexes is greater than the free hydrazone–oxime (H2L,1), and there is a good agreement between the practical and theoretical data. The thermogravimetric investigation shows that the complexes break down in two to four decomposing steps in temperature range extended from 50 to 1000°C. In vitro antimicrobial activity data demonstrated an increase in activity of the hydrazone–oxime (H2L,1), upon chelation, and some metal complexes show enhanced antibacterial and antifungal agents.