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This paper describes the synthesis of two beta-phosphorylamide ligands and their coordination chemistry with the Ln ions Tb3+, Eu3+, and Sm3+. Both the ligands and Ln complexes were characterized by IR, NMR, MS, and X-ray crystallography. The luminescence properties of the Tb3+ and Eu3+ complexes were also characterized, including the acquisition of lifetime decay curves. In the solid state, the Tb3+ and Sm3+ ligand complexes were found to have a 2:2 stoichiometry when analyzed by X-ray diffraction. In these structures, the Ln ion was bound by both oxygen atoms of each beta-phosphorylamide moiety of the ligands. The Tb3+ and Eu3+ complexes were modestly emissive as solutions in acetonitrile, with lifetime values that fell within typical ranges. 

Interest in the isolation and recovery of lanthanide and actinide metals has gained recent attention due to their increasing use in everyday materials ( e.g. batteries, screens, sensors) as well as their application in alternative energy production ( e.g. nuclear power). However, the purification of these metals, both from recycled materials and raw sources, is daunting due to the similar chemical properties of these elements. This review focuses on the use of supramolecular, preorganized organic ligands as extraction agents in liquid–liquid extraction systems to achieve the separation and recovery of f-elements. For the purposes of this review, “supramolecular ligands” are those that append two or more chelating groups to a scaffold. The synthesis of each ligand is presented, along with selections of the extraction results from each compound. When appropriate, the extraction results of the supramolecular, preorganized ligands are compared with their monomeric, commercial counterparts. 

Four tripodal carbamoylmethylphosphine oxide (CMPO)-based ligands are reported here and assessed with regard to lanthanide (Ln) coordination chemistry and selective extraction of lanthanide ions from aqueous solution. Inspired by previous liquid–liquid extraction studies that suggested a preference for terbium( iii ), the current work further probes the extraction behavior of a tris-(2-aminoethyl)amine (TREN) capped, ethoxy substituted CMPO ligand with respect to the entire series of lanthanides. Upon confirmation of Tb 3+ extraction selectivity versus the whole series, experiments were conducted to assess the effect of increasing the alkyl chain length within the ligand TREN cap, as well as changing the CMPO substituents by replacing the ethoxy groups with more hydrophobic phenyl groups to promote solubility in the organic extraction solvent. Extraction efficiencies remained low for most lanthanides upon increasing the cap size, with % E values consistently around 5%, and a complete loss of Tb 3+ preference was noted with a decrease in % E from 18% to 3.5%. For the agent employing the original, smaller TREN cap but with phenyl substituents on the CMPO units, an increase in extraction toward the middle of the row was again observed, albeit modest, with relatively high % E values for both Gd 3+ and Tb 3+ versus the other lanthanides (13 and 11%, respectively). A more dramatic extraction selectivity for the phenyl substituted ligand was achieved upon modification of the ligand to metal ratio, with a 100 : 1 ratio resulting in a near linear decrease in % E from 41% for La 3+ to 3.7% for Lu 3+ . Finally, modification of the TREN capping scaffold by adding an oxygen atom to the central nitrogen led to consistently low % E values, revealing the effect of TREN cap oxidation on Ln extraction for this tripodal CMPO ligand system. 

We report here the characterization in solution (NMR, luminescence, MS) and the solid-state (X-ray crystallography, IR) of complexes between phenacyldiphenylphosphine oxide and five Ln( iii ) ions (Sm, Eu, Gd, Tb, Dy). Four single crystal X-ray structures are described here showing a 1 : 2 ratio between the Ln 3+ ions Eu, Dy, Sm and Gd and the ligand, where the phosphine oxide ligands are bound in a monodentate manner to the metal center. A fifth structure is reported for the 1 : 2 Eu(NO 3 ) 3 -ligand complex showing bidentate binding between the two ligands and the metal center. The solution coordination chemistry of these metal complexes was probed by 1 H, 13 C and 31 P NMR, mass spectrometry, and luminescence experiments. The title ligand has the capability to sensitize Tb 3+ , Dy 3+ , Eu 3+ and Sm 3+ leading to metal-centered emission in solutions of acetonitrile and methanol and in the solid state.