Electrochemical and spectroscopic studies of some less stable oxidation states of selected lanthanide and actinide elements

Hobart, David E.

doi:10.2172/6364847

Cited by 5 publications

(4 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, these periodic trends, especially the standard reduction potentials, are almost exclusively obtained from aqueous media, and some of these data again would not withstand contemporary scrutiny. Finally, even though many of these values are available in compendia that long ago gathered dust, − a careful examination of postcurium data shows that much of it is not actually known and is based on rudimentary extrapolations. , …”

Section: Introductionmentioning

confidence: 99%

Electrochemical Studies of Selected Lanthanide and Californium Cryptates

et al. 2019

View full text Add to dashboard Cite

Efforts to quantitatively reduce CfIII → CfII in solution as well as studies of its cyclic voltammetry have been hindered by its scarcity, significant challenges associated with manipulating an unusually intense γ emitter, small reaction scales, the need for nonaqueous solvents, and its radiolytic effects on ligands and solvents. In an effort to overcome these impediments, we report on the stabilization of CfII by encapsulation in 2.2.2-cryptand and comparisons with the readily reducible lanthanides, Sm3+, Eu3+, and Yb3+. Cyclic voltammetry measurements suggest that CfIII/II displays electrochemical behavior with characteristics of both SmIII/II and YbIII/II. The °E 1/2 values of −1.525 and −1.660 V (vs Fc/Fc+ in tetrahydrofuran (THF)) for [Cf(2.2.2-crypt)]3+/2+ and [Sm(2.2.2-crypt)]3+/2+, respectively, are similar. However, the ΔE values upon complexation by 2.2.2-cryptand for CfIII/II more closely parallels YbIII/II with postencapsulation shifts of 705 and 715 mV, respectively, whereas the shift of SmIII/II (520 mV) mirrors that of EuIII/II (524 mV). This suggests more structural similarities between CfII and YbII in solution than with SmII that likely originates from more similar ionic radii and local coordination environments, a supposition that is corroborated by crystallographic and extended X-ray absorption fine structure measurements from other systems. Competitive-ion binding experiments between EuIII/II, SmIII/II, and YbIII/II were also performed and show less favorable binding by YbIII/II. Connectivity structures of [Ln(2.2.2-cryptand)(THF)][BPh4]2 (Ln = EuII, SmII) are reported to show the important role that THF plays in these redox reactions.

show abstract

Section: Introductionmentioning

confidence: 99%

Electrochemical Studies of Selected Lanthanide and Californium Cryptates

et al. 2019

View full text Add to dashboard Cite

show abstract

“…In both the works of Hobart et al [41] and Varlashkin et al [44] with electrochemical deposition and coprecipitation, terbium-containing solids were obtained. However, since the obtained material was noncrystalline, no XRD data was presented.…”

Section: Stability Studiesmentioning

confidence: 99%

“…Adjusting the hydroxide ion concentration to ~ 1 M stabilizes Tb(IV), which can be observed by the color change from colorless to a dark, reddish-brown solution. Tb(IV) is characterized by UV-Vis absorption spectra with a broad-band absorption centered about 365 nm [41,42].…”

Section: Electrochemical Oxidation Of Tb 3+ In Various Aqueous Mediamentioning

confidence: 99%

“…However, Tb(IV) and Pr(IV) are unstable in aqueous solutions due to their very positive formal reduction potentials (+3.1 V and +3.2 V vs. SHE, respectively), resulting in their back reduction to the trivalent states by reaction with water. Only limited experimental information on stabilization of tetravalent terbium in aqueous solutions is available in the literature [41][42][43][44][45][46][47],…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electrochemical oxidation of terbium(III) in aqueous media: influence of supporting electrolyte on oxidation potential and stability

et al. 2022

View full text Add to dashboard Cite

Apart from the generally dominant trivalent oxidation state, several lanthanides can occur in divalent or tetravalent states as well. Changing the valence state alters the chemical properties and therefore gives the opportunity to ease intragroup lanthanide separations. The hydrated terbium(III) ion has a highly positive reduction potential (E 0 = + 3.1 V vs. SHE), but it can be oxidized to its tetravalent state and via ozonolysis or electrolysis and stabilized in highly concentrated carbonate solutions. In this study, terbium(III) is electrochemically oxidized to terbium(IV) in aqueous carbonate, nitrate and periodate media. Spectroscopic and elemental analysis were done to characterize terbium(IV) and to gain insight in the stability of these complexes in the aqueous electrolytes of carbonate, nitrate and periodate. In all these electrolytes, oxidation and stabilization were achieved at different pH, terbium concentration, salt concentration and applied potentials. The most promising electrolyte was found to be carbonate, since it allowed to attain more concentrated and more stable terbium(IV) solutions.

show abstract