Complexation and molecular modeling studies of europium(III)–gallic acid–amino acid complexes

• The stability constants of Eu(III)–gallic acid complexes were determined.
• The antioxidant gallic acid has formed strong complexes with Eu(III) ion.
• The interaction of Eu–gallic acid complexes with some amino acids was studied.
• The pKa values of gallic acid and amino acids were predicted using COSMO-RS model.
• The geometries of Eu–gallic acid complexes were characterized by DFT.

With many metal-based drugs extensively used today in the treatment of cancer, attention has focused on the development of new coordination compounds with antitumor activity with europium(III) complexes recently introduced as novel anticancer drugs. The aim of this work is to design new Eu(III) complexes with gallic acid, an antioxida'nt phenolic compound. Gallic acid was chosen because it shows anticancer activity without harming health cells. As antioxidant, it helps to protect human cells against oxidative damage that implicated in DNA damage, cancer, and accelerated cell aging. In this work, the formation of binary and ternary complexes of Eu(III) with gallic acid, primary ligand, and amino acids alanine, leucine, isoleucine, and tryptophan was studied by glass electrode potentiometry in aqueous solution containing 0.1 M NaNO3 at (298.2 ± 0.1) K. Their overall stability constants were evaluated and the concentration distributions of the complex species in solution were calculated. The protonation constants of gallic acid and amino acids were also determined at our experimental conditions and compared with those predicted by using conductor-like screening model for realistic solvation (COSMO-RS) model. The geometries of Eu(III)–gallic acid complexes were characterized by the density functional theory (DFT). The spectroscopic UV–visible and photoluminescence measurements are carried out to confirm the formation of Eu(III)–gallic acid complexes in aqueous solutions.

Developing new Eu(III) complexes with gallic acid, an antioxidant phenolic compound. The Eu(III)–gallic acid complex could be a promising chemotherapeutic drug due to its high stability in aqueous solution.Figure optionsDownload as PowerPoint slide