Substituent Effect on Cytotoxicity and Interaction Profile of DNA/BSA With Selected Terpyridine Derivatives of Ester/Ferrocene and Their Fe(III) and Ru(III) Complexes—A Comparative Analysis

Abstract

The present work demonstrates the synthesis of ester and ferrocene groups containing new terpyridine-based ligands (FRL and RL) and their selected meal complexes FR-Fe, FR-Ru, RL-Fe, and RL-Ru. Investigations on the influence of the ester and ferrocene groups on binding to DNA/BSA and anticancer activity were carried out. All these products were structurally characterized by using spectroscopic and analytical techniques. Notably, the molecular structures of both the ligands and the ester-based Fe(III) complex were confirmed by single-crystal X-ray diffraction analysis. Additionally, theoretical calculations were employed to further establish the structures of the synthesized ligands and their metal complexes, which were subsequently utilized for molecular docking studies to evaluate their binding potential. The docking results revealed the best binding orientation with the lowest possible binding energy of −10.20 kcal/mol for the RL-Fe complex with BSA and −8.30 kcal/mol for the FR-Fe complex with DNA. Furthermore, the binding interactions of all the synthesized compounds were investigated using UV–visible absorption (UV) and fluorescence spectroscopy (FL). The binding sites and binding constants were determined using the Stern-Volmer equation. Moreover, cytotoxicity assays were performed against lung cancer (A549), liver cancer (Hep G2), and normal Vero cell lines, with results benchmarked against cisplatin. Notably, the ligand (FRL) exhibited significant cytotoxic action with an IC₅₀ of 54.51 μM compared to the related Fe(III) complex (FR-Fe) (i.e., 69.86 μM) against A549 cells. But the complex FR-Fe displayed IC₅₀ of 56.19 μM against Hep G2 cells, demonstrating better potency over cisplatin.