Back to Basics: Lanthanide and Heavy Actinide Chelation at High pH by Niobium Polyoxometalates
Makenzie T Nord1, Doctor Stephen1, May Nyman1
1Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States.
Abstract:
Niobium polyoxometalates (Nb-POMs) form in alkaline media, which limits their use as ligands for acidic cations, particularly lanthanides and actinides. Metal-Nb-POM moieties have the potential for emergent and enhanced properties, based on strong complexation behavior and high stability of the resultant materials. Here, we probe interactions of lanthanides (Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+) and actinides (Am3+, Cm3+) with a Nb-POM [Nb6O19]8- (Nb6) in alkaline media. Nb6, the most charge-dense Nb-POM, enhances f-element luminescence emission by up to × 106, via Nb-POM-mediated sensitization. Lengthened emission lifetimes correlate with the release of the metal-cation hydration sphere, replaced by multidentate Nb-POMs. The Nb6-Ln(An) complexes resist carbonate and phosphate displacement, and Nb6-Ln(An) complexation is retained upon isolation of the solids from solution. Electrospray ionization mass spectrometry (ESI-MS) and Raman spectroscopy both indicate the formation of the unprecedented Peacock-Weakley Nb-POM ([LnIII(Nb5O18)2]19-) in addition to simple Nb6-Ln coordination complexes. Luminescence emission spectra support the presence of simple Nb6-Ln coordination complexes. Small-angle X-ray scattering (SAXS) evidence the formation of Ln-Nb-POM aggregates. This foundational investigation highlights the potential of Nb-POMs as metal-ligands at basic pH, with value-added properties including scaffolding extended materials and controlling light absorption and emission.
More Related Videos
08:13Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area
Published on: February 19, 2018
13:21Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
Related Concept Videos
Complexation Equilibria: The Chelate Effect
Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
Complexometric Titration: Ligands
Extraction: Advanced Methods
Complexation Equilibria: Factors Influencing Stability of Complexes
Valence Bond Theory
