Molecular dysprosium complexes for white-light and near-infrared emission controlled by the coordination environment

A series of single-molecule dysprosium (Dy³⁺) complexes consisting of β-diketonate ligands, L₁ = 4,4,4-trifluoro-1-phenyl-1,3-butadionate and L₂ = 4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butadionate, as water-containing complexes, and the auxiliary triphenylphosphine oxide (tppo) ligand as water-free complexes were investigated as potential white-light emitters. The coordination environment and choice of the ligands play an important role in the behavior of the yellow/blue emission of the Dy³⁺ complexes (Y: ⁴F_9/2 → ⁶H_13/2 – yellow, and B: ⁴F_9/2 → ⁶H_15/2 and ligand phosphorescence – blue) based on the sensitization efficiency of the Dy³⁺ ion by the ligands. By introducing the auxiliary tppo ligand in the complex, the relative intensity of the Dy³⁺ emission increases due to a more efficient sensitization of the Dy³⁺ ion. The CIE (Commission International d'Eclairage) coordination at room temperature for water-containing, DyL₁H₂O (0.340, 0.333), and DyL₂H₂O (0.270, 0.249), and for water-free complexes, DyL₁tppo (0.364,0.391) and DyL₂tppo (0.316, 0.331), are close to the coordinates of ‘ideal’ white light (0.333, 0.333). The CCT (Correlated Color Temperature) values at room temperature for DyL₁H₂O (5129 K), DyL₂H₂O (18,173 K), and DyL₂tppo (6319 K) correspond to ‘cold-white-light’ emitters, while the DyL₁tppo (4537 K) matches a ‘warm-white-light’ emitter. Beside emitting in the visible (Vis) region, the Dy³⁺ complexes also show emission in the near-infrared (NIR) part of spectrum, which has been studied in detail.