Synthesis, Characterization, Molecular Docking, and Antimicrobial Activities of Dinuclear Nickel(II) Palladium(II), and Platinum(IV) Complexes

Abstract

The Schiff base of benzidinedioxime was synthesized by the condensation reaction of benzidine with diacetylmonoxime in acid media. The chemical structure, electronic properties, and crystal structure of benzidinedioxime were investigated by several physicochemical techniques. These included Fourier transform-infrared (FTIR), UV−visible spectrophotometry, nuclear magnetic resonance (NMR), and powder X-ray diffraction (PXRD). FT-IR and elemental analysis of benzidinedioxime are consistent with chemical formulas. The NMR analyses have shown two peaks in different chemical shifts of the diphenyl and dimethyl groups in different environments.The PXRD of benzidinedioxime demonstrated that space groups are triclinic with P1 (1) point groups. UV-Vis spectrum of benzidinedioxime revealed smooth and strong peaks due to electronic, vibration, and rotation transitions indicated by n→σ*, n→п*, and п→п* electronic transition. Nickel(II), palladium(II), and platinum(IV) complexes were synthesized by reacting the metal ion with benzidinedioxime in a 1:1 mole ratio. Elemental and 1H-nuclear morganatic resonance results showed that two benzidinedioxime ligands are coordinated to two Ni(II) and Pd(II) ions via the nitrogen atoms of both the oxime groups and azomethine group. In the platinum(IV) dinuclear complex, benzidinedioxime coordinates via the four oxygen atoms of oxime groups and azomethine. Powder X-ray diffraction (PXRD) indicated that nickel(II) chloride and platinum(IV) chloride complexes have six-coordinate octahedral geometry. In contrast,palladium(II) acetate and nickel(II) acetate complexes have four-coordinate square planar and tetrahedron geometry, respectively. Molecular docking studies confirmed that the nickel(II) complex is the most potent dual dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) bacterial enzyme inhibitor. The receptor of the DHPS enzyme (PDB: 3ZTE) showed the best interaction with the nickel(II) complex in comparison to a receptor of the DHFR enzyme (PDB: 3FRB) and aminoglycoside enzymes family. All synthesized complexes and ligands exhibited significant results against PS. Aeruginous than their corresponding sulfamethoxazole-trimethoprim (SMX-TMP) drug. The nickel(II) complex possessed the highest antimicrobial activity against tested microorganisms among the three synthesized complexes.