Reduction in Coordination Number of Eu(III) on Complexation with Pyrazine Mono- and Di-Carboxylates in Aqueous Medium

Dumpala, Rama Mohana Rao; Boda, Anil; Kumar, Pranaw; Rawat, N.S.; Ali, Sk. Musharaf

doi:10.1021/acs.inorgchem.9b01772

Cited by 22 publications

(7 citation statements)

References 48 publications

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“…The graphical solution of the above eq in the form of h νi vs n avg for the complexation of Th(IV) with HEIDA was shown in Figure in which h νi is the heat released in the complexation per mole of metal ion with the ligand and n avg is the average number of ligand HEIDA bound per metal ion. The stepwise enthalpy changes for formation ML, ML 2 , and ML 3 can be deduced from the plot of h vi vs n avg (Figure b) at n avg = 1, 2, and 3, respectively. ,,− Further, the Gibbs free energy changes and successive entropy changes are calculated by stepwise enthalpy changes and the corresponding log K values using the equation …”

Section: Resultsmentioning

confidence: 99%

Solution Thermodynamics for the Thorium Complexation with N-(2-Hydroxyethyl) Iminodiacetic Acid

2020

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N-(2-Hydroxyethyl)iminodiacetic acid (HEIDA-H 2 ) is one of the major chelating agents present in the mixed nuclear waste of the Hanford site. The complexation of thorium with HEIDA-H 2 in aqueous medium was investigated to understand the capability of HEIDA-H 2 to affect the migration of actinides from the waste storage sites. The present studies aimed at determining the thermodynamic parameters of Th(IV)−HEIDA complexes to know the speciation, stability (log K) and strength of bond formations (enthalpy and entropy changes) by potentiometric and calorimetric titrations, respectively. Thorium forms ML, ML 2 and ML 3 complexes with HEIDA. The obtained log K values 11.25 ± 0.10, 9.24 ± 0.10, and 8.1 ± 0.10, are higher than the complexes of thorium with monodenatate ligands (simple carboxylates), bidentate ligands (aminomonocarboxylates, dicarboxylates), and heterodicarboxylates. The very high entropy values of the Th(IV)−HEIDA complexes in comparison to the Th(IV) complexes with structurally similar ligands reflects the stronger complexation of Th with HEIDA over others. HEIDA acts as a tridentate ligand forming two five-membered chelates through the two carboxylate oxygens and the nitrogen with thorium, while the hydroxyethl group was found to enhance the stabilization by indirect participation. Density functional theory was used to optimize the geometries and to determine the thermodynamic parameters, bond distances and partial charges on individual atoms for the experimentally predicted complexes. The theoretical predictions are found to be in agreement with the experimental observations.

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Section: Resultsmentioning

confidence: 99%

Solution Thermodynamics for the Thorium Complexation with N-(2-Hydroxyethyl) Iminodiacetic Acid

2020

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“…Isothermal calorimetric titration studies were done to reveal the kind and extent of interaction of the ligand bis(phosphoramidate) with Th(IV). The electrical and chemical calibration of the instrument prior to the actual experiment was carried out as per the reported procedure . The ligand solution was added in equal increments of 10 μL via a syringe into a fixed volume (2.7 mL) of thorium (0.001 mol L –1 ) to obtain the heat profile data (power vs time) as shown in Figure S5a in †ESI.…”

Section: Resultsmentioning

confidence: 99%

Selective Extraction of Thorium(IV) from Uranium and Rare Earth Elements Using Tetraphenylethane-1,2-diylbis(phosphoramidate)

et al. 2023

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Tetraphenylethane-1,2-diylbis(phosphoramidate) in conjugation with a room temperature ionic liquid in chloroform medium is reported for the first time in the liquid–liquid extraction of thorium (Th). The extracted Th(IV) is collected as a white solid in the organic medium, thereby facilitating its easy separation. A high distribution ratio (D) of (12.4 ± 0.1) × 103 in 2–8 mol L–1 acidity range and high decontamination factors (α) of Th(IV) from uranium, lanthanides, and a number of transition elements makes this extraction process versatile and selective. A number of experimental investigations in synergism with extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) studies are interpreted to confirm the structure of the chelated complex. A 1:2 metal/ligand complex in which the two oxygen and two nitrogen atoms of each bis(phosphoramidate) molecule satisfying the eight coordination sites of Th(IV) is found to be formed. The extracted white solid thorium complex is easily converted to ThO2 after washing and heating at 1300 °C under O2 atmosphere. This work is expected to find direct application in the thorium fuel cycle, especially in the mining process of thorium from its ores and in the separation of fissile 233U from fertile 232Th in irradiated fuel.

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“…The chemical nature of the participating ligand and the geometry arrived by its coordination on the equatorial plane has phenomenal effects on the intensities and positions of electronic transitions of the uranyl ion in the range of 380–480 nm arising from vibronic perturbed electronic transitions. , The protonation process is an inseparable mechanism while studying the complexation phenomenon, − especially with the protonated/deprotonated ligands; and the protonation thermodynamic data are a prerequisite to obtain the complexation thermodynamics data. The present studies utilized the protonation data from our previous work .…”

Section: Resultsmentioning

confidence: 99%

Chemical and Redox Speciation of Uranyl with Three Environmentally Relevant Bifunctional Chelates: Multi-Technique Approach Combined with Theoretical Estimations

et al. 2022

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Carbon and phosphorous are two primary elements common to the bio-geosphere and are omnipresent in both biotic and abiotic arenas. Phosphonate and carboxylate are considered as building blocks of glyphosate and humic substances and constituents of the cellular wall of bacteria and are the driving functionalities for most of the chemical interactions involving these two elements. Phosphonocarboxylates, a combination of both the functionalities in one moiety, are ideal models to dig deep into for understanding the chemical interactions of the two functional groups with metal ions. Phosphorous and carbon majorly exist as inorganic/organic phosphate and carboxylate, respectively, in the bio-geosphere. Aquatic contamination is a major concern for uranium, and the presence of complexing agents would alter the uranium concentrations in aquifers. Determination of solution thermodynamic parameters, speciation plots, redox patterns, E h −pH diagrams, coordination structures, and molecular-level understanding by density functional theory calculations was carried out to interpret the uranyl (UO 2 2+ ) interaction with three environmentally relevant phosphonocarboxylates, namely, phosphono-formic acid (PFA), phosphono-acetic acid (PAA), and phosphono-propanoic acid (PPA). UO 2 2+ forms 1:1 complexes with the three phosphonocarboxylates in the monoprotonated form, having nearly the same stability, and the complexes [UO 2 (PFAH)], [UO 2 (PAAH)], and [UO 2 (PPAH)] involve chelate formation of five, six, and seven membered rings, respectively, through the participation of an oxygen each from the carboxylate and phosphonate, strengthened by an intra-molecular hydrogen bonding through the proton of the phosphonate moiety with uranyl oxygen. The complex formations are favored both enthalpically and entropically, with the latter being more contributive to the overall free energy of formation. The redox speciation showed an aqueous soluble complex formation over a wide pH range of 1−8. Electrospray ionization mass spectrometry and extended X-ray absorption fine structure established the coordination modes, which are further corroborated by density functional calculations. The knowledge gained from the present studies provide potential inputs in framing the cleanup, sequestering, microbial, and bio-remediation strategies for uranyl from aquatic environments.

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Reduction in Coordination Number of Eu(III) on Complexation with Pyrazine Mono- and Di-Carboxylates in Aqueous Medium

Cited by 22 publications

References 48 publications

Solution Thermodynamics for the Thorium Complexation with N-(2-Hydroxyethyl) Iminodiacetic Acid

Solution Thermodynamics for the Thorium Complexation with N-(2-Hydroxyethyl) Iminodiacetic Acid

Selective Extraction of Thorium(IV) from Uranium and Rare Earth Elements Using Tetraphenylethane-1,2-diylbis(phosphoramidate)

Chemical and Redox Speciation of Uranyl with Three Environmentally Relevant Bifunctional Chelates: Multi-Technique Approach Combined with Theoretical Estimations

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