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Lanthanide and Actinide Ion Complexes Containing Organic Ligands Investigated by Surface-Enhanced Infrared Absorption
Sakiko Hirata1, Ryoji Kusaka2, Shogo Meiji1
1Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Hiroshima739-8526, Japan.
Inorganic Chemistry
|December 22, 2022
Summary
Surface-enhanced infrared absorption (SEIRA) spectroscopy was used to study lanthanide (Ln) and actinide (An) complexes. This technique provides structural insights into ion complexation and selective extraction processes.
Area of Science:
- Coordination Chemistry
- Spectroscopy
- Nuclear Chemistry
Background:
- Lanthanide (Ln) and actinide (An) separation is crucial in nuclear fuel reprocessing and waste management.
- Organic ligands like diglycolamide (DGA), Cyanex-272, and N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN) are vital for selective Ln/An extraction.
- Understanding the structural basis of ligand-metal interactions is key to optimizing separation processes.
Purpose of the Study:
- To develop and apply surface-enhanced infrared absorption (SEIRA) spectroscopy for structural investigation of Ln and An complexes.
- To explore the coordination behavior of DGA, Cyanex-272, and TPEN derivatives with Ln and An ions.
- To establish a link between spectroscopic data and solvent extraction behavior for selective Ln/An separation.
Main Methods:
- Synthesis of thiol-functionalized organic ligands (DGA, Cyanex-272, TPEN analogs) for surface immobilization.
- Attachment of ligands to a gold-coated silicon prism via S-Au covalent bonds to create SEIRA substrates.
- Complexation of Eu3+, Gd3+, Tb3+ (Ln) and Am3+ (An) ions with surface-bound ligands and analysis using Fourier transform infrared (FTIR) spectroscopy in attenuated total reflection (ATR) mode.
Main Results:
- A novel sample preparation method for SEIRA allowed analysis of small ion solution volumes (5 μL), beneficial for radiotoxic Am3+.
- Complexation of Ln and An ions with DGA caused a red shift (approx. 20 cm-1) in the C=O stretching vibration band.
- The magnitude of the C=O band shift correlated inversely with reported solvent extraction equilibrium constants, indicating coordination ability assessment.
Conclusions:
- SEIRA spectroscopy is a powerful tool for the structural characterization of Ln and An ion complexes.
- The study provides microscopic insights into the selective extraction mechanisms of lanthanides and actinides.
- The developed SEIRA method offers a sensitive and efficient approach for studying metal-ligand interactions relevant to separation science.
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