Americium

Runde, Wolfgang; Schulz, W.W.

doi:10.1007/978-94-007-0211-0_8

Cited by 17 publications

(18 citation statements)

References 442 publications

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“…Am(III) shows a hypersensitive 7 F 0 → 5 L 6 transition at 503 nm, and due to its high extinction coefficient, this ion is highly suitable for UV–vis spectroscopy . In presence of MAL, the band shows a continuous redshift to 506 nm with increasing pH from 1–6 (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation

et al. 2018

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The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi-method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (log β0, Δr H 0 m, Δr S 0 m, Δr G 0 m) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X-ray absorption fine structure spectroscopy complemented with quantum-mechanical ab initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes. The metal is coordinated by two carboxylate groups and a hydroxyl group. UV–vis, laser fluorescence, and calorimetric studies consistently yielded two complex species having a 1:1 and a 1:2 (metal/malate) stoichiometry. Parallel factor analysis and iterative transformation factor analysis were applied to decompose experimental spectra into their single components and to determine stability constants. The 1:1 and 1:2 Nd(III) malate complexation constants determined by isothermal titration calorimetry were extrapolated to zero ionic strength using the specific ion interaction theory, yielding log β1 0 and log β2 0 of about 6 and 9, respectively. The respective complexation enthalpies Δr H 0 m,1 and Δr H 0 m,2 showed average values of 5 kJ·mol–1 which are typical for small organic molecules. The comparison of Nd(III) and Am(III) malate complexes showed that the malate binding motif, the speciation, and the thermodynamics can be transferred from lanthanides(III) to actinides(III) supporting the 4f/5f element homology.

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Section: Resultsmentioning

confidence: 99%

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation

et al. 2018

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“…A primary goal of the work reported here is to assess stabilities of OSs, particularly the pentavalent OS, of the actinides Cm, Bk, and Cf. These elements represent the transition from the early actinides that exhibit higher OS, including Am VI and possibly also Am VII , to the latest actinides, Es through Lr, that have been definitively identified only in the An II and/or An III OS. The meagre realm of OSs for the late actinides may not be entirely due to intrinsic chemistry because synthetic efforts for these elements have been very limited due to scarcity and short half-lives of available synthetic isotopes.…”

Section: Introductionmentioning

confidence: 99%

Pentavalent Curium, Berkelium, and Californium in Nitrate Complexes: Extending Actinide Chemistry and Oxidation States

et al. 2018

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Pentavalent actinyl nitrate complexes AnO(NO) were produced by elimination of two NO from An(NO) for An = Pu, Am, Cm, Bk, and Cf. Density functional theory (B3LYP) and relativistic multireference (CASPT2) calculations confirmed the AnO(NO) as AnO actinyl moieties coordinated by nitrates. Computations of alternative AnO(NO) and AnO(NO) revealed significantly higher energies. Previous computations for bare AnO indicated AnO for An = Pu, Am, Cf, and Bk, but CmO: electron donation from nitrate ligands has here stabilized the first Cm complex, CmO(NO). Structural parameters and bonding analyses indicate increasing An-NO bond covalency from Pu to Cf, in accordance with principles for actinide separations. Atomic ionization energies effectively predict relative stabilities of oxidation states; more reliable energies are needed for the actinides.

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“…Even with incomplete bioactivation, the DTPA intermediates possess multiple coordination sites to chelate metals in the blood. This potential is exemplified in the established relationship between the number of coordination sites on a chelating agent and the binding of 241 Am . The tri‐ethyl ester of DTPA, with five coordination sites, represents the DTPA intermediate in the urine with the fewest number of coordination sites.…”

Section: Discussionmentioning

confidence: 99%

Orally Administered DTPA Penta-Ethyl Ester for the Decorporation of Inhaled 241Am

Sueda

Sadgrove

Huckle

et al. 2014

Journal of Pharmaceutical Sciences

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Diethylenetriaminepentaacetic acid (DTPA) is an effective decorporation agent to facilitate the elimination of radionuclides from the body, but its permeability-limited oral bioavailability limits its utility in mass-casualty emergencies. To overcome this limitation, a prodrug strategy using the penta-ethyl ester form of DTPA is under investigation. Pharmacokinetic and biodistribution studies were conducted in rats by orally administering [14C]DTPA penta-ethyl ester, and this prodrug and its hydrolysis products were analyzed as a single entity. Compared to a previous reporting of intravenously administered DTPA, the oral administration of this prodrug resulted in a sustained plasma concentration profile with higher plasma exposure and lower clearance. An assessment of the urine composition revealed that the bioactivation was extensive but incomplete, with no detectable levels of the penta- or tetra-ester forms. Tissue distribution at 12 h was limited, with approximately 73% of the administered dose being associated with the gastrointestinal tract. In the efficacy study, rats were exposed to aerosols of 241Am nitrate before receiving a single oral treatment of the prodrug. The urinary excretion of 241Am was found to be 19% higher than with the control. Consistent with prior reports of DTPA, the prodrug was most effective when the treatment delays were minimized.

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Americium

Cited by 17 publications

References 442 publications

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation

Pentavalent Curium, Berkelium, and Californium in Nitrate Complexes: Extending Actinide Chemistry and Oxidation States

Orally Administered DTPA Penta-Ethyl Ester for the Decorporation of Inhaled 241Am

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