Design, Synthesis and Biological Profiling of Fe(III)–Bipyridine Schiff Base Complexes: Experimental, Computational and Pharmacokinetic Insights

Abstract

Schiff base ligands and their transition metal complexes continue to attract attention for their versatile coordination behavior and biological relevance. Herein, three thiosemicarbazone ligands (L1–L3) were synthesized from para-nitrobenzaldehyde and substituted thiosemicarbazides and converted to their corresponding iron(III)–bipyridine complexes (FT1–FT3). The compounds were characterized by FT–IR, UV–vis, ¹H/¹³C NMR, ESI–MS, EPR, molar conductivity, and elemental analysis. Spectroscopic data confirmed coordination through the azomethine nitrogen and thione sulfur, evidenced by shifts in characteristic bands and new Fe─N and Fe─S vibrations. DFT optimization revealed a distorted octahedral geometry and provided HOMO–LUMO gaps, global reactivity descriptors, and molecular electrostatic potential maps. Anticancer (SiHa), antimycobacterial, and antifungal assays showed that FT3 was the most active, giving 72.85% antifungal inhibition at 1000 ppm together with improved anticancer and antibacterial activity. Molecular docking against HPV-18 E2 (PDB 1F9F) and CYP51 (PDB 1EA1) gave favorable binding energies that correlated with the experimental trends, FT3 forming the most stable interactions. ADME predictions indicated broadly acceptable, though preliminary, pharmacokinetic behavior. Overall, these iron(III) Schiff base complexes display promising multi-target activity warranting further mechanistic and preclinical study.