Lanthanide complexes with phosphine oxides: synthesis, luminescence and magnetism

Abstract

Lanthanide-based molecular materials have become the focus of attention in numerous fields of research, such as molecular magnetism or luminescence, due to their unique intrinsic properties. This TFG presents the synthesis and structural, magnetic, and luminescent characterization of a family of molecular complexes based on lanthanide (III) cations. The complexes are formed by the reaction of different lanthanide salts with a phosphine oxide ligand, dppmO2. These complexes present a neutral mononuclear structure with a nonacoordinated central lanthanide ion by nine O-donor atoms. This structure has been authenticated by X-Ray crystal diffraction of the 5-Tb complex, where the coordination geometry can be described as a monocapped square antiprism. The magnetic measurements revealed that all the complexes, with the exception of 4-Gd, exhibit high intrinsic single ion anisotropy determined through the D parameter calculated by static measurements. Furthermore, dynamic magnetic measurements demonstrated that 4-Gd, 5-Tb, 8-Yb complexes exhibit slow relaxation of their magnetization, as evidenced by their out-of-phase susceptibility (𝜒’’) as a response to an alternating current magnetic field. The fitting of the dynamic measurements has been performed to elucidate the relaxation mechanisms causing the complexes to lose their magnetization. Complex 5-Tb follows a purely Raman process, whereas 4-Gd and 8-Yb follow a combination between Raman and quantum tunnelling processes. These relaxation mechanisms are mediated by spin-phonon interaction. Finally, the luminescent measurements revealed visible intrinsic luminescence for both 3-Eu and 5-Tb, indicating that dpmO2, despite being a chromophore, do not perform an efficient effect as sensitizer.