Fe(III), Ni(II), and Cu(II)-moxifloxacin-tri-substituted imidazole mixed ligand complexes: Synthesis, structural, DFT, biological, and protein-binding analysis

Abstract

Herein, three new mixed-ligand complexes were synthesized through the reaction of Fe(III), Ni(II) and Cu(II) with moxifloxacin (MOX) in the presence of tri-substituted imidazole (TSI) to investigate their antibacterial, antifungal, and antioxidant potential. Elemental analysis, molar conductivity, electronic spectra, infrared spectroscopy, mass spectrometry, magnetic studies, thermal gravimetric investigations have been utilized for insuring the chelation process and structural elucidation. Results revealed that MOX and TSI interact with the metal ions via the (carbonyl oxygen and the carboxylic oxygen) and (hydroxyl oxygen and imidazole-ring nitrogen) atoms for MOX, and TSI, respectively. Octahedral geometries have been proposed for the Fe(III), Ni(II) complexes, while a distorted tetrahedral geometry was proposed for the Cu(II) complex. The proposed structures had been optimized via Density functional theory (DFT) calculations. Moreover, the frontier molecular orbitals (FMOs), in terms of HOMO and LUMO, and the molecular electrostatic potential (MEP) were obtained. Furthermore, the energy gap, chemical hardness, softness, chemical potential, electrophilicity index were evaluated. The antimicrobial potential was in vitro investigated against some common pathogenic bacterial and fungal strains; moreover, the antioxidant activity was evaluated using DPPH method. Results revealed that the three synthesized complexes had high antimicrobial activity against all tested phytopathogens and a significant antioxidant potential, compared to the free ligands. Furthermore, the in vitro potential was validated utilizing molecular docking investigation against four target receptors: 5JQ9, 6CLV, 3CKU, and 5IJT. The molecular docking results showed that Fe(III), Ni(II), and Cu(II) complexes had the highest activity towards the 5JQ9, (6CLV and the 3cku), and 5IJT receptors, respectively.