Synthesis, characterization of europium(III) and terbium(III) complexes containing lawsone ligand and their interaction with DNA, HSA, and topoisomerases

Abstract

In this study, two complexes based on Europium [Eu(LAW)₃(H₂O)₃] (1) and Terbium [Tb(LAW)₃(H₂O)₃] (2), each containing the lawsone ligand, were synthesized and comprehensively characterized using Infrared and UV-Visible spectroscopies, Cyclic Voltammetry, Conductivity, and Magnetic Susceptibility measurements. Crystal structure information was determined via X-ray diffraction (XRD), and elemental analysis confirmed the compounds’ purity. Experimental and theoretical UV-Vis data were compared through TD-DFT calculations, providing insights into the low luminescence of both Eu(III) and Tb(III) complexes, with excited states calculated both with and without solvent effects. DNA-binding experiments with ct-DNA were conducted using viscosity measurements, UV-Vis titrations, circular dichroism, and fluorescence competition assays to explore the complexes' primary interactions with the DNA target. Additionally, DNA cleavage properties were examined using pBR322 plasmid DNA with agarose gel electrophoresis. Although no cleavage activity was observed, DNA interaction studies suggested covalent binding, supported by viscosity and circular dichroism data. Furthermore, analyzing the docking results, both compounds demonstrated stable conformations within the Sudlow I site also the lawsone-based compounds demonstrated an ability to bind to human serum albumin (HSA) with binding constants (K_b) in the range of 10⁵-10⁶ and showed Topoisomerase IIα inhibition at 50 µM. Both compounds remained stable for up to 48 hours.