Infrared spectra and structures of the Th(OH)2 and Th(OH)4 molecules

Investigation of Chelating Agents for the Removal of Thorium from Human Teeth upon Nuclear Contamination

Thorium-232 (232Th) is a radioactive heavy metal that is of increasing interest as a source of nuclear energy. However, upon nuclear incidents, the ingestion or inhalation of Th in major quantities can contribute to chemical and radiological health problems, including accumulation in the bone tissue and an increased risk of developing pancreatic, lung, and hematopoietic cancers. The major mineral component of the bone is hydroxyapatite (HAP)─also the major mineral component of the teeth. As such, the teeth are the first site of exposure upon oral ingestion of Th-contaminated materials, and Th can pose a potential risk to teeth development. In essence, in the case of human contamination, it is critical to identify effective chelating agents capable of removing Th. Using a batch study methodology, this present work investigates the uptake and the removal of Th from synthetic HAP and from teeth samples by diethylenetriamine pentaacetate (DTPA), ethylenediaminetetraacetic acid (EDTA), and other promising chelating agents. Th uptake over synthetic HAP exceeds 98% at physiological pH with <1 min of contact time and uptake exceeds 90% across the entire pH range. Regarding teeth, over 1 mg Th uptaken per gram of tooth is observed after 24 h. The overall effectiveness of chelating agents for the removal of Th from is as follows: DTPA > EDTA > NaF/mouthwash/3,4,3-LI(1,2-HOPO); this trend was observed both in synthetic HAP and Th-impregnated teeth samples.

Reactions of Thorium Oxide Clusters with Water: The Effects of Oxygen Content

Thorium oxide has many important applications in industry. In this article, theoretical calculations have been carried out to explore the hydrolysis reactions of the ThO_n (n=1-3) clusters. The reaction mechanisms of the O-deficient ThO and the O-rich ThO₃ are compared with the stoichiometric ThO₂ . The theoretical results show good agreement with the prior experiments. It is shown that the hydrolysis mainly occurred on the singlet potential surface. The overall reactions consist of two hydrolysis steps which are all favourable in energy. The effects of oxygen content on the hydrolysis are elucidated. Interestingly, among them, the peroxo group O₂ ^2- in ThO₃ is converted to the HOO- ligand, behaving like the terminal O^2- in the hydrolysis which is transformed into the HO- groups. In addition, natural bond orbital (NBO) analyses were employed to further understand the bonding of the pertinent species and to interpret the differences in hydrolysis.

The effects of pH on U(VI)/Th(IV) and Ra(II)/Ba(II) adsorption by polystyrene-nano manganese dioxide composites: Fourier Transform Infra-Red spectroscopic analysis

Fourier Transform Infra-Red (FTIR) spectroscopy provides structural information of prime importance to understand ions coordination to adsorbents. This consequently aids in the design of improved ion exchange materials and help in deriving the optimum adsorption conditions. In the present work, the adsorption mechanism of both U(VI)/Th(IV) and Ra(II)/Ba(II) radionuclides couples onto polystyrene-nano manganese dioxide (PS-NMO) composite is reported in relation to the effect of working solution pH. The separation of each radionuclide couple; i.e. U(VI)/Th(IV) and Ra(II)/Ba(II); could be effectively achieved at pH = 3 and pH = 1 respectively. The pH values not only determine the species of the respected elements that are mainly present in aqueous solution before applying the adsorbent, but it also alters the structure of the composite adsorbent. FTIR spectroscopy showed that Th(IV) formed inner sphere complexes and occupied the A site in the dioxide layer, while U(VI) formed outer sphere complexes on the surface of the composite. Spectra subtraction showed that some aromatic bands and vinyl C-H bands were split or shifted to lower wavenumbers with the loading of Ba(II). This was attributed to changes in the composite stereochemistry to accommodate Ba(II). The working solution pH could be the key in the separation process of both U(VI)/Th(IV) and Ra(II)/Ba(II) from their mixture, and FTIR spectroscopy stands as a useful technique to explain the difference between metal ions responses to adsorbants.

Mononuclear thorium halide clusters ThX4 (X = F, Cl): gas-phase hydrolysis reactions

Density functional theory (DFT) calculations have been performed to explore the gas-phase hydrolysis reaction of mononuclear thorium halide clusters ThX4 (X = F, Cl). We have found that the hydrolysis of ThCl4 is easier than that of ThF4. Furthermore, their hydrolysis reactions favor pathways of direct dehydration of Th(OH)4 instead of further hydrolysis of ThOX2. There are some differences between the hydrolysis of ThCl4 and that of MCl4 (M = Ti, Zr and Hf). The X-HY (X = F, Cl; Y = F, Cl and OH) hydrogen bonds play an important role in the hydrogen transfer process of the hydrolysis reaction. The differences in the steric effects and bonding may be important factors that are related to the disparities in the hydrolysis of the above-mentioned metal halides.

Properties of Cerium Hydroxides from Matrix Infrared Spectra and Electronic Structure Calculations

Reactions of laser ablated cerium atoms with hydrogen peroxide or hydrogen and oxygen mixtures diluted in argon and condensed at 4 K produced the Ce(OH)3 and Ce(OH)2 molecules and Ce(OH)2(+) cation as major products. Additional minor products were identified as the Ce(OH)4, HCeO, and OCeOH molecules. These new species were identified from their matrix infrared spectra with D2O2, D2, and (18)O2 isotopic substitution and correlating observed frequencies with values calculated by density functional theory. We find that the amounts of Ce(OH)3 and of the Ce(OH)2(+) cation increase on UV (λ > 220 nm) photolysis, while Ce(OH)2, Ce(OH)4, and HCeO are photosensitive. The observed major species for Ce are in the +III or +II oxidation state, and the minor product, Ce(OH)4, is in the +IV oxidation state. The calculations for the vibrational frequencies with the B3LYP functional agree well with the experiment. The NBO analysis shows significant backbonding to the metal 4f and 5d orbitals for the closed shell species. Most open shell species have the excess spin in the 4f with paired spin in the 5d due to backbonding. The heats of formation of the observed species were derived from the available data from experiment and the calculated reaction energies. The major products in this study are different from similar reactions for Th where the tetrahydroxide was the major species.

Reaction of Laser-Ablated Uranium and Thorium Atoms with H2Se: A Rare Example of Selenium Multiple Bonding

The compounds H2ThSe and H2USe were synthesized by the reaction of laser-ablated actinide metal atoms with H2Se under cryogenic conditions following the procedures used to synthesize H2AnX (An = Th, U; X = O, S). The molecules were characterized by infrared spectra in an argon matrix with the aid of deuterium substitution and electronic structure calculations at the density functional theory level. The main products, H2ThSe and H2USe, are shown to have a highly polarized actinide-selenium triple bond, as found for H2AnS on the basis of electronic structure calculations. There is an even larger back-bonding of the Se with the An than found for the corresponding sulfur compounds. These molecules are of special interest as rare examples of multiple bonding of selenium to a metal, particularly an actinide metal.

Dimethylsilyl bis(amidinate)actinide complexes: synthesis and reactivity towards oxygen containing substrates

Ligand1reacts with ThCl₄and UCl₄yielding complexes2and4, respectively. Complex3is obtained from complex2displaying extremely short Th–OH bond distances.

Infrared Spectrum and Structure of Thorimine (HNThH2)

Laser-ablated thorium atoms react with ammonia to form thorimine (NH=ThH(2)), the first actinide imine to be reported. This work underscores the high reactivity of thorium atoms, particularly for N-H bond activation, reveals a new type of multiple bond to actinide atoms, and shows that this bond is strong for thorium as a result of an important contribution from the f orbitals.

Experimental and Theoretical Investigations of IR Spectra and Electronic Structures of the U(OH)2, UO2(OH), and UO2(OH)2 Molecules

Reactions of laser-ablated U atoms and H2O2 molecules produce UO2, H2UO2, and UO2(OH)2 as major products and U(OH)2 and HU(O)OH as minor products. Complementary information is obtained from similar reactions of U atoms with D2O2, with H2 + O2 mixtures, and with H2O in excess Ar. Through extensive relativistic density functional theory calculations, we have determined the geometry structures and ground states of these U species with a variety of oxidation states U(II), U(IV), U(V), and U(VI). The calculated vibrational frequencies, IR intensities, and isotopic frequency ratios are in good agreement with the experimental values, thus supporting assignments of the observed matrix IR spectra. We propose that the reactions proceed by forming an energized [U(OH)4] intermediate from reactions of the excited U atom with two H2O2 molecules. Because of the special stability of the U(VI) oxidation state, this intermediate decomposes to the UO2(OH)2 molecule, which reveals a distinctive difference between the chemistries of U and Th, where the major product in analogous Th reactions is the tetrahedral Th(OH)4 molecule owing to the stable Th(IV) oxidation state.