Synthesis, Characterization, DFT, Biological and Molecular Docking of Mixed Ligand Complexes of Ni(II), Co(II), and Cu(II) Based on Ciprofloxacin and 2-(1H-benzimidazol-2-yl)phenol

In the present work, three new Cobalt(II) (CPFX1), Nickel(II) (CPFX2), and Copper (II) (CPFX3) complexes based on Ciprofloxacin (CPFX), and 2-(1H-benzimidazol-2-yl)phenol (2-Bip) were successfully prepared and characterized. The structures were established with the aid of elemental analysis, molar conductance, Electronic spectra, Infra-Red, and mass spectra, in addition to magnetic studies and thermal gravimetric analyses. The results suggest that the Ciprofloxacin (CPFX) and 2-(1H-benzimidazol-2-yl)phenol (2-Bip) ligands behave in the mono-negatively bi-dentate manner through the (Carboxylic Oxygen & pyridine-ring Oxygen) and (hydroxyl Oxygen & benzimidazole-ring Nitrogen), respectively. Both CPFX1 and CPFX2 complexes were predicted to have tetrahedral structures, while the CPFX3 complex was predicted to have an octahedral structure. Quantum chemistry simulations based on density functional theory (DFT) were used to optimize the suggested structures and investigate the nature of the frontier orbitals through frontier molecular orbital (FMO) analysis. These calculations were used to assign sites on the molecules' surfaces using a molecular electrostatic potential map and understand the structure and reactivity behavior using calculated global reactivity descriptors. The antibacterial activity of the prepared complexes was screened in vitro using two Gram-positive bacteria (Bacillus cereus (+ve) and Staphylococcus aureus (+ve)) and two Gram-negative bacteria (Escherichia coli (-ve)) and Pseudomonas aeruginosa (-ve)). For in vitro antifungal testing, Candida albicans and Aspergillus flavus were used. Using the 2,2-Di Phenyl Picryl Hydrazyl (DPPH) assay, we checked the ligands and complexes for their potential antioxidant characteristics. It has been shown that the CPFX1, CPFX2 and CPFX3 complexes are biologically more efficient than the antibiotic CPFX-free ligand. Molecular docking was utilized to determine the most probable main binding paths of the coordination compounds to the microbial enzymes, concluding the biological investigation. Molecular docking simulations were performed on the target proteins Escherichia coli and Staphylococcus aureus, in addition to Aspergillus flavus, and the Crystal Structure of Human Peroxiredoxin 2 Oxidized. The substrate enzyme interacts with the compounds in question by several methods, including H-bonding, and ionic interactions.

Automated summary

In this study, three new complexes based on Ciprofloxacin (CPFX) and 2-(1H-benzimidazol-2-yl)phenol (2-Bip) were prepared and characterized. The structures were determined using various analytical techniques, and the ligands exhibited mono-negatively bi-dentate behavior. Quantum chemistry simulations were performed to optimize the structures and investigate the frontier orbitals. The prepared complexes showed enhanced antibacterial activity and antioxidant characteristics compared to the free ligand CPFX.