Electro‐kinetic Separation of Rare Earth Elements Using a Redox‐Active Ligand

Fang, Hanming; Cole, Bren E.; Qiao, Yusen; Bogart, Justin A.; Cheisson, Thibault; Manor, Brian C.; Carroll, Patrick J.; Schelter, Eric J.

doi:10.1002/ange.201706894

Cited by 21 publications

(15 citation statements)

References 23 publications

(14 reference statements)

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“…Finally, the proposed effect of Ln III coordination on the E m of PQQ in XoxF 43 suggests the feasibility of performing electrochemical separations of REs using RE-PQQ complexes, as has been accomplished recently with other redox-active ligands. 13 The speciation of aqueous Ln III -PQQ complexes is heterogeneous, 76,77 but such an approach may be possible with the help of PQQ-binding proteins. Another open question is whether lanthanoenzymes that are not PQQ-dependent exist.…”

Section: ■ Lanthanoenzymesmentioning

confidence: 99%

The Chemistry of Lanthanides in Biology: Recent Discoveries, Emerging Principles, and Technological Applications

2019

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The essential biological role of rare earth elements lay hidden until the discovery in 2011 that lanthanides are specifically incorporated into a bacterial methanol dehydrogenase. Only recently has this observation gone from a curiosity to a major research area, with the appreciation for the widespread nature of lanthanide-utilizing organisms in the environment and the discovery of other lanthanide-binding proteins and systems for selective uptake. While seemingly exotic at first glance, biological utilization of lanthanides is very logical from a chemical perspective. The early lanthanides (La, Ce, Pr, Nd) primarily used by biology are abundant in the environment, perform similar chemistry to other biologically useful metals and do so more efficiently due to higher Lewis acidity, and possess sufficiently distinct coordination chemistry to allow for selective uptake, trafficking, and incorporation into enzymes. Indeed, recent advances in the field illustrate clear analogies with the biological coordination chemistry of other metals, particularly CaII and FeIII, but with unique twists—including cooperative metal binding to magnify the effects of small ionic radius differences—enabling selectivity. This Outlook summarizes the recent developments in this young but rapidly expanding field and looks forward to potential future discoveries, emphasizing continuity with principles of bioinorganic chemistry established by studies of other metals. We also highlight how a more thorough understanding of the central chemical question—selective lanthanide recognition in biology—may impact the challenging problems of sensing, capture, recycling, and separations of rare earths.

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Section: ■ Lanthanoenzymesmentioning

confidence: 99%

The Chemistry of Lanthanides in Biology: Recent Discoveries, Emerging Principles, and Technological Applications

2019

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“…27 Recently, we showed that the use of a tris-hydroxylamine ligand (H 3 TriNOx, tris(2-tert-butylhydroxylamine)benzylamine) 28 displayed differences in the oxidation rates within (RE)-TriNOx complexes modulated by the Lewis acidity of the RE cation, which afforded efficient electro-kinetic separations of RE = Eu, Y, Yb, and Lu (Chart 1). 29 This approach represents a new method for separating RE ions; separations of REs are typically achieved through thermodynamic differences, for example, through differences in affinities for a specific ligand. 30 As such, further development of kinetic-based separations remains a challenging but compelling research opportunity.…”

Section: ■ Introductionmentioning

confidence: 99%

Redox-Driven Chelation and Kinetic Separation of Select Rare Earths Using a Tripodal Nitroxide Proligand

et al. 2019

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Separation of the rare-earth (RE) elements (Sc, Y, La–Lu) is challenging because of their similar chemical properties, but is necessary for their applications in renewable energy and electronic device technologies. The development of separation processes driven by kinetic factors represents a new area for this field. Herein, we disclose a novel method of separating select rare earths by reacting RE cyclopentadienides with the triradical species tris(2-tert-butylnitroxyl)benzylamine (1). The key proligand 1 was characterized using a variety of techniques including X-ray crystallography, magnetometry, and EPR spectroscopy. When applied to an equimolar mixture of La:Y cyclopentadienide complexes, different rates of chelation of these organometallic precursors by 1 were observed, affording a separation factor of 26 under the reported conditions.

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“…37 Employing the ability of TriNOx 3− to undergo ligand-based oxidation, we also demonstrated the separation of heavy/heavy RE pairs by an electro-kinetic method. 38 In both cases, the key contributions were the elucidation of a molecular basis to achieve separation of RE pairs. The factor responsible for the exceptional selectivity for some RE pairs of this seminal system, namely, selective selfassociation for light RE pairs, is also its main limitation for extension to other RE pairs, especially for LRE/LRE or HRE/ HRE combinations of REs.…”

Section: ■ Introductionmentioning

confidence: 99%

Phosphoryl-Ligand Adducts of Rare Earth-TriNOx Complexes: Systematic Studies and Implications for Separations Chemistry

Cheisson

Cole

Manor

et al. 2019

ACS Sustainable Chem. Eng.

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Phosphoryl ligands of the general formula OPR3 (R = Me, OMe, Et, n Bu, Ph, i Pr, NMe2) were coordinated to [Nd(TriNOx)] (TriNOx3– = ([(2- t BuNO)C6H4CH2]3N)3–), and the resulting complexes were characterized. Solution equilibrium constants for each complex were determined, demonstrating a large range for phosphoryl ligands’ Lewis basicity. Thermogravimetric analyses provided evidence for the qualitative thermodynamic preference of phosphoryl ligands for [Nd(TriNOx)] over the dysprosium analogue. These findings were exploited for the separation of binary mixtures of neodymium/dysprosium and lanthanum/neodymium. Implementation of phosphoryl ligands in the TriNOx separation system expands its scope and demonstrates a fundamentally different mode for separating rare-earth cations based on adducts with neutral donors.

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Electro‐kinetic Separation of Rare Earth Elements Using a Redox‐Active Ligand

Cited by 21 publications

References 23 publications

The Chemistry of Lanthanides in Biology: Recent Discoveries, Emerging Principles, and Technological Applications

The Chemistry of Lanthanides in Biology: Recent Discoveries, Emerging Principles, and Technological Applications

Redox-Driven Chelation and Kinetic Separation of Select Rare Earths Using a Tripodal Nitroxide Proligand

Phosphoryl-Ligand Adducts of Rare Earth-TriNOx Complexes: Systematic Studies and Implications for Separations Chemistry

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