Theoretical study of the influence of electron push or pull bipyridine ligands on the electronic structure of Eu3+ ibuprofenate complexes

Abstract

In this work, we showed the influence of dissubstituted bipyridine ligands with electron push or pull groups in the structural and electronic properties of the Eu3+ ibuprofenate complexes. QTAIM-DFT analyzes performed for the sixteen complexes demonstrated that the interaction between the 6,6′-X-bpy ligands and the Eu3+ ion is strongly weakened when X = –OCH3 (complex 10) and –NO2 (complex 16) due to steric hindrances and a decrease in ligand basicity. The Gibbs free energy of the formation of these complexes is less favored around 27 kcal mol−1 compared to complex 3 (X = 5,5′-NH2-bpy), which is the most thermodynamically stable structure. The calculated absorption bands in the ultraviolet region revealed that bpy ligands containing strongly electron donating groups shift the maximum absorption wavelength towards the near visible region. These results suggest that the studied Ln3+ ion complexes may be used in molecular devices with optoelectronic applications in the visible region.