Synthesis, characterization, and biological evaluation of zinc(II) complexes with benzohydrazide derivative and phosphine ligands

Abstract

New zinc(II) complexes of the mixed ligands were synthesized using a benzohydrazide derivative (L), yielded from reaction of benzohydrazide and isatin, in combination with (Phen) and various phosphine co-ligands, including 1,10-phenanthroline (Phen), 1,2-bis(diphenylphosphino)ethane(dppe), 1,2-bis(diphenylphosphino) propane (dppp), and triphenylphosphine (PPh₃).  Characterization methods included molar conductivity, atomic absorption, FTIR, and ¹H, ¹³C{¹H},³¹P{¹H}-NMR spectroscopy, confirming tetrahedral geometry around zinc(II) with the ligand N'-(2-oxoindolin-3-ylidene) benzohydrazide (L) acting as a bidentate chelating ligand. The thermogravimetric (TG) analysis of the papered complexes [Zn(L)(Phen)]Cl₂, [Zn(L)(PPh₃)]Cl₂, and [Zn(L)(dppp)]Cl₂ showed that each of them has been decomposed in three stages. The in vitro biological activities were evaluated against four types of bacteria, Staphylococcus aureus, Streptococcus faecalis, Pseudomonas aeruginosa, and Escherichia coli, along with cancer human liver (Hep-G2) cell lines, revealing that the complexes exhibited significant cytotoxicity. Notably, the [Zn(L)(Phen)]Cl₂ complex showed the strongest inhibitory effect on human liver (Hep-G2) cells, with an IC₅₀ of 31.12 ± 1.57 μM. Antibacterial tests indicated that [Zn(L)(Phen)]Cl₂ and [Zn(L)(dppp)]Cl₂ complexes effectively inhibited Streptococcus faecalis, and [Zn(L)(Phen)]Cl₂ also had limited efficacy against Gram-negative bacteria. Structure-activity relationship studies highlighted that the choice of phosphine ligand significantly influences the biological properties of these zinc(II) complexes.

KEY WORDS: Antibacterial, Anticancer, Benzohydrazide derivative, Mixed ligands complexes, Phosphines, Spectroscopy

Bull. Chem. Soc. Ethiop. 2025, 39(2), 313-326.                                                              

DOI: https://dx.doi.org/10.4314/bcse.v39i2.10