Fe(III) and Ni(II) Imidazole-Benzimidazole Mixed-Ligand Complexes: Synthesis, Structural Characterization, Molecular Docking, DFT Studies, and Evaluation of Antimicrobial and Anti-Inflammatory Activities

Abstract

This work delves into the synthesis, characterization, and bioactivity of new metal complexes of Imidazole-based ligand (IM) and a Benzimidazole-based ligand (BZ) with Fe(III) and Ni(II) ions. A broad scope of characterization techniques, including elemental analysis, IR spectroscopy, magnetic moment measurement, electronic spectrum, mass spectrometry, thermal analysis, and DFT calculations, ensured the successful preparation of the complexes, establishing a 1:1:1 (M:IM:BZ) stoichiometry. Both the NiBZIM and FeBZIM complexes possessed octahedral geometry with coordinated one water and two waters of Fe(III) and Ni(II), respectively. Calculation by the DFT model demonstrated that the reduction of energy gap and rise of softness for the metal complexes resulted due to metal coordination, enhancing reactivity and forecasted biological activity of the complexes. FeBZIM and NiBZIM complexes exhibited strong antimicrobial activity, whereas both complexes displayed improved efficacy towards Gram-positive as well as Gram-negative bacteria compared to their corresponding free ligands. Their activities were comparable to the standard antibiotic Chloramphenicol. Furthermore, these complexes also exhibited good antifungal activity towards Aspergillus niger as well as Candida albicans, surpassing the free ligands. MIC values also ensured enhanced antimicrobial activity of the metal complexes. Other than these operations, the complexes demonstrated great anti-inflammatory activity of which FeBZIM complex was the strongest with a direction towards the reference drug IC50. Molecular docking against E. coli FabH–CoA complex (PDB ID: 1HNJ) and Human Cyclooxygenase-2 (COX-2) (PDB ID: 5IKT) that the FeBZIM complex exhibited the best binding affinity with the establishment of several hydrogen bonds with key amino acid residues, suggesting a favorable antibacterial activity. Overall, the newly synthesized FeBZIM and NiBZIM complexes demonstrate immense potential as novel antimicrobial and anti-inflammatory drugs with enhanced efficacy relative to their free ligands.