Luminescence of Lanthanide Complexes with Perfluorinated Alkoxide Ligands.

Four groups of rare-earth complexes, comprising 11 new compounds, with fluorinated O-donor ligands ([K(THF)][Ln(OCF)(THF)] (; Ln = Ce, Nd), K[Ln(OCF)(THF)] (; Ln = Eu, Gd, Dy), [K(THF)][Ln(pin)(THF)] (; Ln = Ce, Nd), and [K(THF)][Ln(pin)(THF)] (; Ln = Eu, Gd, Dy, Y) have been synthesized and characterized. Single-crystal X-ray diffraction data were collected for all compounds except . Species , , and are uncommon examples of six-coordinate (Eu, Gd, Dy, and Y) and seven-coordinate (Ce and Nd) Ln centers in all-O-donor environments. Species , , , and are all luminescent (except where Ln = Gd and Y), with the solid-state emission of being exceptionally blue-shifted for a Ce complex. The emission spectra of the six Nd, Eu, and Dy complexes do not show large differences based on the ligand and are generally consistent with the well-known free-ion spectra. Time-dependent density functional theory results show that and undergo allowed 5f → 4d excitations, consistent with luminescence lifetime measurements in the nanosecond range. Eu-containing and , however, were found to have luminescence lifetimes in the millisecond range, indicating phosphorescence rather than fluorescence. The performance of a pair of multireference models for prediction of the Ln = Nd, Eu, and Dy absorption spectra was assessed. It was found that spectroscopy-oriented configuration interaction as applied to a simplified model in which the free-ion lanthanide was embedded in ligand-centered Löwdin point charges performed as well (Nd) or better (Eu and Dy) than canonical NEVPT2 calculations, when the ligand orbitals were included in the treatment.