Computationally-Guided Assignment of Unexpected Signals in the Raman Spectra of Uranyl Triperoxide Complexes

2019

Angew Chem Int Ed

Section: Figuresupporting

confidence: 61%

In Situ Generation of Organic Peroxide to Create a Nanotubular Uranyl Peroxide Phosphate

Kravchuk

2019

Angew Chem Int Ed

“…Empirical band predictions based upon bond distances do not accurately predict vibrational frequency, indicating a need for additional computational approaches. Quantum considerations that were developed by Vallet et al [141] and utilized by Dembowski [138] for the peroxide system provided better agreement between the predicted (717 cm −1 ) and experimental (710 cm −1 ) values.…”

Section: Chemical and Structural Elucidation Of Uranium Solid-state Cmentioning

confidence: 96%

“…Similarly, uranyl peroxide spectra contain overlapping modes from uranyl and peroxide stretches. The peroxide mode frequency depends on the coordination to uranyl polyhedra and ranges from 904 to 822 cm −1 [137,138]. In the case of LiK 3 [(UO 2 ) 4 (O 2 ) 2 (C 10 H 12 O 8 N 2 ) 2 (H 2 O) 2 ]·18 H 2 O, two partially resolved vibrational features are located near 830 cm −1 [139].…”

Section: Chemical and Structural Elucidation Of Uranium Solid-state Cmentioning

confidence: 99%

Detection and identification of solids, surfaces, and solutions of uranium using vibrational spectroscopy

Haes

Coordination Chemistry Reviews

2018

133

128

The purpose of this review is to provide an overview of uranium speciation using vibrational spectroscopy methods including Raman and IR. Uranium is a naturally occurring, radioactive element that is utilized in the nuclear energy and national security sectors. Fundamental uranium chemistry is also an active area of investigation due to ongoing questions regarding the participation of 5f orbitals in bonding, variation in oxidation states and coordination environments, and unique chemical and physical properties. Importantly, uranium speciation affects fate and transportation in the environment, influences bioavailability and toxicity to human health, controls separation processes for nuclear waste, and impacts isotopic partitioning and geochronological dating. This review article provides a thorough discussion of the vibrational modes for U(IV), U(V), and U(VI) and applications of infrared absorption and Raman scattering spectroscopies in the identification and detection of both naturally occurring and synthetic uranium species in solid and solution states. The vibrational frequencies of the uranyl moiety, including both symmetric and asymmetric stretches are sensitive to the coordinating ligands and used to identify individual species in water, organic solvents, and ionic liquids or on the surface of materials. Additionally, vibrational spectroscopy allows for the in situ detection and real-time monitoring of chemical reactions involving uranium. Finally, techniques to enhance uranium species signals with vibrational modes are discussed to expand the application of vibrational spectroscopy to biological, environmental, inorganic, and materials scientists and engineers.

“…Zuschriften tolerance.T his is likely due to the significant overlap of the bands and the presence of the broad benzaldehyde dimethyl acetal feature.Peaks within this region are consistent with the formation of organic peroxide molecules (860-870 cm À1 )and uranyl peroxide complexes. [18,30] After two hours,t he same spectral features are present, but the band intensities have again changed. Them ost noticeable feature is the new band at 830 cm À1 ,w hich is likely ar esult of reaching equilibrium conditions for the benzaldehyde/benzaldehyde dimethyl acetal reaction.…”

Section: Angewandte Chemiementioning

confidence: 96%

In Situ Generation of Organic Peroxide to Create a Nanotubular Uranyl Peroxide Phosphate

Kravchuk

2019

Angewandte Chemie

Current synthetic pathwaysf or uranyl peroxide materials introduce high initial concentrations of aqueous H 2 O 2 that decline over time.Alternatively,insitu generation of organic peroxide would maintain constant concentrations of peroxideo ver prolonged periods of time and open new pathwayst on ovel uranyl peroxide compounds.H erein, we demonstrate this concept through the synthesis of ananotubelike uranyl peroxide phosphate (NUPP), Na 12 [(UO 2 )(m-O 2 )-(HPO 4 )] 6 (H 2 O) 40 ,making use of the inhibited autoxidation of benzaldehyde in benzyl alcohol solutions in the presence of phosphonate ligands.The unique feature of NUPP is the bent dihedral angle U-(m-O 2 )-U (123.98 8 AE 0.48 8 to 124.68 8 AE 0.58 8), which allows hexameric uranyl peroxide macrocycles to adopt the nanotubular topology and prevents the formation of nanocapsules.R aman spectroscopyo ft he solution phase confirms our mechanistic understanding of the reaction pathway and confirms that consistent levels of peroxidea re generated in situ over an extended period of time.Uranium peroxide solids were first synthesized from aqueous solutions in 1876 and additional literature precedent supports their prevalence in diverse chemical environments. [1] Early work focused on the formation of uranyl peroxides in engineered systems (e.g.l ight-water reactors), [2,3] but am ore thorough understanding of these phases began with the characterization of the naturally occurring peroxide-containing minerals studtite and metastudtite. [4] Uranium ore deposits emit a-radiation, which can radiolytically split water molecules into hydroxyl and superoxide radicals and ultimately form solid uranyl peroxide phases. [5,6] Additional findings demonstrate that uranyl peroxides are ac omponent of yellow cake [7] and form as an alteration phase on spent fuel rods and corium lavas at the Chernobyl site. [8,9] Based upon the persistence of these phases,u nderstanding the chemistry and speciation of uranyl peroxide compounds in complex systems is of high importance.An expansive number of synthetic uranyl peroxide phases and nanocapsules have been characterized by Burns and coworkers, [6,10,11,13] with additional experimental and computational studies providing ab asis for the formation mechanism. [12] Self-assembly of the nanocapsules is dependent on ab ent dihedral angle for the U-(m-O 2 )-U bond (134.88 8 to 158.48 8) [13] that allows for the required curvature in the spherical, scaphoid, or ellipsoid clusters.D iversity within this system is driven by the ratio of m 2 -OH/m 2 -O 2 bridges, identity of the alkali countercations,a nd presence of inorganic or organic chelators.S ynthetic pathways for these laboratory-based compounds rely upon the direct addition of 30 %a queous H 2 O 2 solution. [13][14][15][16] Shocking the chemical system with high initial amounts of H 2 O 2 under basic conditions results in rapid decomposition [17] and off-gassing during synthesis that decrease the free peroxide concentration over as hort period of time. [16,18] This increases the diversit...