Exploring the influence of bis-phosphine ligands on lanthanide complexes: A DFT study

Abstract

This study employs density functional theory (DFT) calculation to investigate the bis-phosphine ligands interaction with lanthanide ions (La3+, Nd3+, Eu3+, Er3+ and Lu3+). Two distinct bridging modes are explored between two phosphine ligands: pyridine and methylene functional groups. The aim is to understand the structural, thermochemical, spectroscopic, and orbital properties of the bis-phosphine-Ln3+ complexes and compare the effects of different bridging modes. It is observed that bis-phosphine ligands form the most stable complexes with Er3+ and the least stable complexes with La3+, as evidenced by interaction energies, Gibb’s free energies and electrophilicity index values. Pyridine-bridged ligands form more stable complexes than methylene-bridged ligands, which is consistent with charge population analysis. Reduced density gradient analysis indicates the presence of strong hydrogen bond-like interactions between lanthanide ions and oxygen/nitrogen atoms of bis-phosphine complexes. Infrared spectra simulations reveal that Er3+ forms stronger bonds with oxygen atoms of bis-phosphine ligands than other lanthanide ions.