Optical Properties of Heavily Fluorinated Lanthanide Tris β-Diketonate Phosphine Oxide Adducts

The construction of lanthanide(III) chelates that exhibit superior photophysical properties holds great importance in biological and materials science. One strategy to increase the luminescence properties of lanthanide(III) chelates is to hinder competitive non-radiative decay processes through perfluorination of the chelating ligands. Here, the synthesis of two families of heavily fluorinated lanthanide(III) β-diketonate complexes bearing monodentate perfluorinated tris phenyl phosphine oxide ligands have been prepared through a facile one pot reaction [Ln(hfac)₃{(Ar^F)₃PO}(H₂O)] and [Ln(F₇-acac)₃{(Ar^F)₃PO}₂] (where Ln = Sm³⁺, Eu³⁺, Tb³⁺, Er³⁺ and Yb³⁺). Single crystal X-ray diffraction analysis in combination with photophysical studies have been performed to investigate the factors responsible for the differences in the luminescence lifetimes and intrinsic quantum yields of the complexes. Replacement of both bound H₂O and C–H oscillators in the ligand backbone has a dramatic effect on the photophysical properties of the complexes, particularly for the near infra-red emitting ion Yb³⁺, where a five fold increase in luminescence lifetime and quantum yield is observed. The complexes [Sm(hfac)₃{(Ar^F)₃PO}(H₂O)] (1), [Yb(hfac)₃{(Ar^F)₃PO}(H₂O)] (5), [Sm(F₇-acac)₃{(Ar^F)₃PO}₂] (6) and [Yb(F₇-acac)₃{(Ar^F)₃PO}₂] (10) exhibit unusually long luminescence lifetimes and attractive intrinsic quantum yields of emission in fluid solution (Φ_Ln = 3.4% (1); 1.4% (10)) and in the solid state (Φ_Ln = 8.5% (1); 2.0% (5); 26% (6); 11% (10)), which are amongst the largest values for this class of compounds to date. View Full-Text