Large Ground-State and Excited-State Crystal Field Splitting of 8-fold-Coordinate Cm3+ in [Y(H2O)8]Cl3·15-crown-5

Lindqvist‐Reis, Patric; Walther, Clemens; Klenze, R.; Eichhöfer, and Andreas; Fanghänel, Thomas

doi:10.1021/jp0574100

Cited by 17 publications

(19 citation statements)

References 30 publications

(60 reference statements)

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“…The strength of the ligand field is determined by the metal to ligand distance and the character of the bond. 36 The large crystal field splitting in aragonite thus correlates to a strong ligand field with low symmetry coordination geometry in good agreement with what is to be expected for structural incorporation on the Ca 2+ lattice site.…”

Section: Curium Luminescence Spectroscopysupporting

confidence: 76%

Incorporation versus adsorption: substitution of Ca2+ by Eu3+ and Cm3+ in aragonite and gypsum

et al. 2009

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The aim of the present work is to understand the interaction behaviour of trivalent f-elements with Ca2+-bearing mineral phases on a molecular level. This is achieved by use of time-resolved laser fluorescence spectroscopy (TRLFS) with Eu3+ and Cm3+ as atomic sensors on a trace concentration level. These ions are of special interest as models for trivalent actinides (e.g., Cm(III), Am(III) or Pu(III)) which strongly contribute to radiotoxicity in high level nuclear waste. Results from TRLFS with these trivalent ions show a significantly different mode of interaction in the two cases: while in aragonite only structural incorporation is observed, on gypsum nothing but inner-sphere surface complexes can be found. This shows how the anions forming the coordination sphere of the foreign ion control the formation of solid solutions as opposed to adsorption complexes.

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Section: Curium Luminescence Spectroscopysupporting

confidence: 76%

Incorporation versus adsorption: substitution of Ca2+ by Eu3+ and Cm3+ in aragonite and gypsum

et al. 2009

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“…At both temperatures the RDF for the first peak occurs at a Cm-O distance of 2.55 Å, which is longer than the one obtained by Yang and Bursten 10 at 298 K, 2.48 Å or that found from EXAFS of Cm(III) solution 2.470(6) 6 or 2.477(5) Å. 7 The second peak occurs at a distance of 4.9 Å, while the one obtained by Yang and Bursten, occurs at 4.7 Å. Their calculations also suggest that the nine water molecules organize themselves into a trigonal bipyramidal configuration of six shorter and three longer bonds.…”

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confidence: 50%

A Quantum Chemical and Molecular Dynamics Study of the Coordination of Cm(III) in Water

et al. 2007

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The study of the behavior of actinide ions in aqueous solution plays a fundamental role in the quest for a better understanding of actinide waste storage problems and separation processes. Considerable progress has been made both experimentally and computationally in recent years, with special attention given to the uranyl ion, 1,2 as well as trivalent lanthanide and actinide ions. Systematic studies of the aqueous trivalent lanthanide ion first coordination sphere show the number of water molecules changes from nine to eight between Pm(III) and Dy(III) at 25°C. Similar behavior is found for the trivalent actinide ions with the transitional region occurring between Am(III) and Es(III). 3,4 Cm(III) 5 is in the middle of the actinide series and provides a bridge between the early actinides and the less common later actinides.Several studies have been performed on this species. Lindqvist-Reis et al. 6 have used time-resolved laser fluorescence spectroscopy to study the hydration of Cm(III) from 20 to 200°C. They found a strong temperature dependence for several of the spectroscopic quantities associated with the 6 D′ 7/2 -8 S′ 7/2 luminescent spectra. The emission band shifts to lower energy with increasing temperature, which is attributed to an equilibrium among hydrated Cm(III) ions with different numbers of water molecules in the first coordination sphere, namely [Cm(H 2 O) 9 ] 3+ and [Cm(H 2 O) 8 ] 3+ . More recently they have also studied 7 the ground-state and excited-state crystal field splitting of 8-fold-coordinate Cm(III) in [Y(H 2 O) 8 Cl 3 .15crown-5] crystals using laser spectroscopy, at temperatures between 20 and 293 K. Skanthakumar et al. 8 and Lindqvist-Reis et al. 9 have analyzed single-crystal X-ray diffraction data from [Cm(H 2 O) 9 ](CF 3 -SO 3 ) 3 to understand the hydration of Cm(III) in solution. According to their studies, the Cm species in the crystal is surrounded by nine coordinating waters with a tricapped-trigonal-prismatic geometry, with six short Cm-O distances at 2.453(1) Å and three longer Cm-O distances at 2.545(1) Å. Skanthakumar et al. 8 also reported high-energy X-ray scattering data for Cm(III) in perchloric acid solution. Two peaks were assigned to the oxygen atoms of H 2 O, the first peak at 2.48(1) Å was from the first coordination shell (8.8(3) oxygen atoms), and the second peak from the second water coordination shell at 4.65(10) Å (13(4) oxygen atoms). Their EXAFS measurements for Cm(III) in perchloric acid suggested that the nine coordinate structure, found in the triflate crystal, persists in solution but with an expanded splitting of the first coordination shell by ∼ 0.07 Å. Yang and Bursten 10 have studied the first and second hydration shells of Cm(III) using quantum chemical and molecular dynamics methods and they have shown that the inclusion of a complete second hydration shell has a significant effect on the primary coordination sphere. To understand the structural and chemical behavior of Cm(III) (and actinyls in general) in solution from a computational perspec...

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“…This analogy is usually attributed to the hardness of the Ln 3+ ions: their coordinations mainly depend upon the steric and electrostatic nature of the ligand interactions 19 . For the same reason, the 4f-block lanthanide elements are also chemical analogues of the 5f-block actinide elements, when at the same oxidation state 20,21,22,23,24,25 . Actually, in the nuclear fuel cycle industry, it is a challenge to separate the Am and Cm actinide activation products from (light) lanthanide fission products in an attempt to eliminate long live radionuclides from radioactive wastes.…”

Section: Introductionmentioning

confidence: 97%

Pair interaction potentials with explicit polarization for molecular dynamics simulations of La3+ in bulk water

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Spezia

et al. 2007

The Journal of Chemical Physics

108

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Pair interaction potentials (IPs) were defined to describe the La(3+)-OH(2) interaction for simulating the La(3+) hydration in aqueous solution. La(3+)-OH(2) IPs are taken from the literature or parametrized essentially to reproduce ab initio calculations at the second-order Moller-Plesset level of theory on La(H(2)O)(8) (3+). The IPs are compared and used with molecular dynamics (MD) including explicit polarization, periodic boundary conditions of La(H(2)O)(216) (3+) boxes, and TIP3P water model modified to include explicit polarization. As expected, explicit polarization is crucial for obtaining both correct La-O distances (r(La-O)) and La(3+) coordination number (CN). Including polarization also modifies hydration structure up to the second hydration shell and decreases the number of water exchanges between the La(3+) first and second hydration shells. r(La-O) ((1))=2.52 A and CN((1))=9.02 are obtained here for our best potential. These values are in good agreement with experimental data. The tested La-O IPs appear to essentially account for the La-O short distance repulsion. As a consequence, we propose that most of the multibody effects are correctly described by the explicit polarization contributions even in the first La(3+) hydration shell. The MD simulation results are slightly improved by adding a-typically negative 1r(6)-slightly attractive contribution to the-typically exponential-repulsive term of the La-O IP. Mean residence times are obtained from MD simulations for a water molecule in the first (1082 ps) and second (7.6 ps) hydration shells of La(3+). The corresponding water exchange is a concerted mechanism: a water molecule leaving La(H(2)O)(9) (3+) in the opposite direction to the incoming water molecule. La(H(2)O)(9) (3+) has a slightly distorded "6+3" tricapped trigonal prism D(3h) structure, and the weakest bonding is in the medium triangle, where water exchanges take place.

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Large Ground-State and Excited-State Crystal Field Splitting of 8-fold-Coordinate Cm³⁺ in [Y(H₂O)₈]Cl₃·15-crown-5

Cited by 17 publications

References 30 publications

Incorporation versus adsorption: substitution of Ca2+ by Eu3+ and Cm3+ in aragonite and gypsum

Incorporation versus adsorption: substitution of Ca2+ by Eu3+ and Cm3+ in aragonite and gypsum

A Quantum Chemical and Molecular Dynamics Study of the Coordination of Cm(III) in Water

Pair interaction potentials with explicit polarization for molecular dynamics simulations of La3+ in bulk water

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