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Heteropolynuclear Lanthanide(III) Complexes for Cooperative Sensitization Upconversion in Water.
Léna Godec1, Richard C Knighton1,2, Nadège Hamon3
1Equipe de Synthèse pour l'Analyse (SynPA), IPHC, UMR 7178, CNRS/Université de Strasbourg, ECPM, 25 Rue Becquerel, 67087 Strasbourg Cedex, France.
Journal of the American Chemical Society
|August 13, 2025
Summary
This study synthesized a novel tritopic ligand (L2) for lanthanide (Ln) complexation, enabling cooperative sensitization upconversion (UC) with enhanced efficiency upon heating. The tetranuclear complex showed the most efficient UC, achieving a 9.0 × 10-7 quantum yield.
Area of Science:
- Coordination Chemistry
- Supramolecular Chemistry
- Photophysics
Background:
- Lanthanide (Ln) complexes are crucial for various applications, including luminescence and catalysis.
- Developing ligands that control Ln coordination and photophysical properties is essential for advanced materials.
- Upconversion (UC) processes in Ln complexes offer unique light-harvesting and emission capabilities.
Purpose of the Study:
- To synthesize and characterize a novel tritopic ligand (L2) capable of binding multiple lanthanide ions.
- To investigate the coordination chemistry and photophysical properties of lanthanide complexes with L2.
- To explore the potential of these complexes in cooperative sensitization upconversion (UC) processes.
Main Methods:
- Synthesis of the tritopic ligand L2 based on tris-functionalized triazacyclononane (tacn) scaffolds and a triethylene glycol linker.
- Coordination of various lanthanide ions (Eu, Tb, Yb, Lu) to the L2 ligand.
- Characterization using NMR and photoluminescent spectroscopies.
- Investigation of UC properties upon Yb excitation at 980 nm.
- Density Functional Theory (DFT) modeling to understand binding interactions.
Main Results:
- Successful synthesis of the tritopic ligand L2 and formation of mono-, di-, tri-, and tetranuclear lanthanide complexes.
- Demonstration of cooperative sensitization upconversion (UC) in Yb-Tb complexes, with visible Tb emission.
- Observation of a significant increase (ca. 10^3) in UC efficiency upon heating due to Ln scrambling.
- Identification of the tetranuclear complex [TbYb(TbYbL2)] as the most efficient UC emitter.
- Achieved a UC quantum yield of 9.0 × 10^-7 at 980 nm excitation.
Conclusions:
- The novel tritopic ligand L2 effectively controls the assembly of polynuclear lanthanide complexes.
- Cooperative sensitization upconversion is efficiently achieved in these complexes, particularly in the tetranuclear species.
- Thermal treatment enhances UC efficiency by promoting lanthanide ion redistribution within the ligand.
- These findings pave the way for developing advanced luminescent materials based on lanthanide coordination complexes.
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