Direct Observation of 4f Intrashell Excitation in Luminescent Eu Complexes by Time-Resolved X‑ray Absorption Near Edge Spectroscopy

We report time-resolved X-ray absorption near edge structure (TR-XANES) measurements at the Eu <i>L</i>₃ edge upon photoexcitation of several Eu^III-based luminescent lanthanide complexes. We find an unambiguous signature of the 4f intrashell excitation that occurs upon energy transfer from the photoactive organic antennas to the lanthanide species. Phenomenologically, this observation provides the basis for direct investigation of a crucial step in the energy transfer pathways that lead to sensitized luminescence in lanthanide-based dyes. Interestingly, the details of the TR-XANES feature suggest that the degree of 4f–5d hybridization may itself vary depending on the excited state of the Eu^III ion

Effects of Ligand Geometry on the Photophysical Properties of Photoluminescent Eu(III) and Sm(III) 1‑Hydroxypyridin-2-one Complexes in Aqueous Solution

A series of 10 tetradentate 1-hydroxy-pyridin-2-one (1,2-HOPO) ligands and corresponding eight-coordinated photoluminescent Eu­(III) and Sm­(III) complexes were prepared. Generally, the ligands differ by the linear (nLI) aliphatic linker length, from 2 to 8 methylene units between the bidentate 1,2-HOPO chelator units. The photoluminescent quantum yields (Φ_tot) were found to vary with the linker length, and the same trend was observed for the Eu­(III) and Sm­(III) complexes. The 2LI and 5LI bridged complexes are the brightest (Φ_totxε). The change in ligand wrapping pattern between 2LI and 5LI complexes observed by X-ray diffraction (XRD) is further supported by density functional theory (DFT) calculations. The bimodal Φ_tot trends of the Eu­(III) and Sm­(III) complexes are rationalized by the change in ligand wrapping pattern as the bridge (<i>n</i>LI) is increased in length

Effects of Ligand Geometry on the Photophysical Properties of Photoluminescent Eu(III) and Sm(III) 1‑Hydroxypyridin-2-one Complexes in Aqueous Solution

A series of 10 tetradentate 1-hydroxy-pyridin-2-one (1,2-HOPO) ligands and corresponding eight-coordinated photoluminescent Eu­(III) and Sm­(III) complexes were prepared. Generally, the ligands differ by the linear (nLI) aliphatic linker length, from 2 to 8 methylene units between the bidentate 1,2-HOPO chelator units. The photoluminescent quantum yields (Φ_tot) were found to vary with the linker length, and the same trend was observed for the Eu­(III) and Sm­(III) complexes. The 2LI and 5LI bridged complexes are the brightest (Φ_totxε). The change in ligand wrapping pattern between 2LI and 5LI complexes observed by X-ray diffraction (XRD) is further supported by density functional theory (DFT) calculations. The bimodal Φ_tot trends of the Eu­(III) and Sm­(III) complexes are rationalized by the change in ligand wrapping pattern as the bridge (<i>n</i>LI) is increased in length