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Otte KS, Niklas JE, Studvick CM, Boggiano AC, Bacsa J, Popov IA, La Pierre HS. Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes. Angew Chem Int Ed Engl 2023; 62:e202306580. [PMID: 37327070 DOI: 10.1002/anie.202306580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 06/15/2023] [Accepted: 06/16/2023] [Indexed: 06/18/2023]
Abstract
The study of the redox chemistry of mid-actinides (U-Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=Pt Bu(pyrr)2 ]- ; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1-M, 2-M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U5+/4+ , U6+/5+ , and to an unprecedented, well-behaved Np5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory.
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Affiliation(s)
- Kaitlyn S Otte
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
| | - Julie E Niklas
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
| | - Chad M Studvick
- Department of Chemistry, The University of Akron, Akron, OH, 44325-3601, USA
| | - Andrew C Boggiano
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
| | - John Bacsa
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
| | - Ivan A Popov
- Department of Chemistry, The University of Akron, Akron, OH, 44325-3601, USA
| | - Henry S La Pierre
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
- Nuclear and Radiological Engineering Program, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA
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Grödler D, Sperling JM, Rotermund BM, Scheibe B, Beck NB, Mathur S, Albrecht-Schönzart TE. Neptunium Alkoxide Chemistry: Expanding Alkoxides to the Transuranium Elements. Inorg Chem 2023; 62:2513-2517. [PMID: 36705531 DOI: 10.1021/acs.inorgchem.2c04338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Two oxo-containing neptunium(IV) tert-butoxides, [Np3O(OtBu)10] (1) and [K4Np2O(OtBu)10] (2), were synthesized using the ligand substitution between neptunium(IV) silylamides and HOtBu, whereas the salt metathesis between [NpCl4(DME)2] (DME = dimethoxyethane) and various amounts of LiOtBu resulted in the formation of oxo-free alkoxides [Np(OtBu)4(py)2] (3; py = pyridine) and [Li(THF)]2[Np(OtBu)6] (4; THF = tetrahydrofuran). These complexes are the first structurally characterized neptunium(IV) alkoxides using single-crystal X-ray diffraction and solid-state absorption spectroscopy, which provide data for the development of anhydrous metal-organic neptunium chemistry.
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Affiliation(s)
- Dennis Grödler
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, 50939 Cologne, Germany
| | - Joseph M Sperling
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Brian M Rotermund
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Benjamin Scheibe
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Nicholas B Beck
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Sanjay Mathur
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, 50939 Cologne, Germany
| | - Thomas E Albrecht-Schönzart
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
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3
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Niklas JE, Studvick CM, Bacsa J, Popov IA, La Pierre HS. Ligand Control of Oxidation and Crystallographic Disorder in the Isolation of Hexavalent Uranium Mono-Oxo Complexes. Inorg Chem 2023; 62:2304-2316. [PMID: 36668669 DOI: 10.1021/acs.inorgchem.2c04056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The development of high-valent transuranic chemistry requires robust methodologies to access and fully characterize reactive species. We have recently demonstrated that the reducing nature of imidophosphorane ligands supports the two-electron oxidation of U4+ to U6+ and established the use of this ligand to evaluate the inverse-trans-influence (ITI) in actinide metal-ligand multiple bond (MLMB) complexes. To extend this methodology and analysis to transuranic complexes, new small-scale synthetic strategies and lower-symmetry ligand derivatives are necessary to improve crystallinity and reduce crystallographic disorder. To this end, the synthesis of two new imidophosphorane ligands, [N═PtBu(pip)2]- (NPC1) and [N═PtBu(pyrr)2]- (NPC2) (pip = piperidinyl; pyrr = pyrrolidinyl), is presented, which break pseudo-C3 axes in the tetravalent complexes, U[NPC1]4 and U[NPC2]4. The reaction of these complexes with two-electron oxygen-atom-transfer reagents (N2O, trimethylamine N-oxide (TMAO) and 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene (dbabhNO)) yields the U6+ mono-oxo complexes U(O)[NPC1]4 and U(O)[NPC2]4. This methodology is optimized for direct translation to transuranic elements. Of the two ligands, the NPC2 framework is most suitable for facilitating detailed bonding analysis and assessment of the ITI. Theoretical evaluation of the U-(NPC) bonding confirms a substantial difference between axially and equatorially bonded N atoms, revealing markedly more covalent U-Nax interactions. The U 6d + 5f combined contribution for U-Nax is nearly double that of U-Neq, accounting for ITI shortening and increased bond order of the axial bond. Two distinct N-atom hybridizations in the pyrrolidine/piperidine rings are noted across the complexes, with approximate sp2 and sp3 configurations describing the slightly shorter P-N"planar" and slightly longer P-N"pyramidal" bonds, respectively. In all complexes, the NPC2 ligands feature more planar N atoms than NPC1, in accordance with a higher electron-donating capacity of the former.
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Affiliation(s)
- Julie E Niklas
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Chad M Studvick
- Department of Chemistry, The University of Akron, Akron, Ohio 44325-3601, United States
| | - John Bacsa
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Ivan A Popov
- Department of Chemistry, The University of Akron, Akron, Ohio 44325-3601, United States
| | - Henry S La Pierre
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States.,Nuclear and Radiological Engineering Program, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
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Goodwin CAP, Wooles AJ, Murillo J, Lu E, Boronski JT, Scott BL, Gaunt AJ, Liddle ST. Carbene Complexes of Neptunium. J Am Chem Soc 2022; 144:9764-9774. [PMID: 35609882 PMCID: PMC9490846 DOI: 10.1021/jacs.2c02152] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Since the advent
of organotransuranium chemistry six decades ago,
structurally verified complexes remain restricted to π-bonded
carbocycle and σ-bonded hydrocarbyl derivatives. Thus, transuranium-carbon
multiple or dative bonds are yet to be reported. Here, utilizing diphosphoniomethanide
precursors we report the synthesis and characterization of transuranium-carbene
derivatives, namely, diphosphonio-alkylidene- and N-heterocyclic carbene–neptunium(III) complexes that exhibit
polarized-covalent σ2π2 multiple
and dative σ2 single transuranium-carbon bond interactions,
respectively. The reaction of [NpIIII3(THF)4] with [Rb(BIPMTMSH)] (BIPMTMSH = {HC(PPh2NSiMe3)2}1–) affords
[(BIPMTMSH)NpIII(I)2(THF)] (3Np) in situ, and subsequent treatment with the N-heterocyclic carbene {C(NMeCMe)2} (IMe4) allows
isolation of [(BIPMTMSH)NpIII(I)2(IMe4)] (4Np). Separate treatment of in situ
prepared 3Np with benzyl potassium in 1,2-dimethoxyethane
(DME) affords [(BIPMTMS)NpIII(I)(DME)] (5Np, BIPMTMS = {C(PPh2NSiMe3)2}2–). Analogously, addition of benzyl
potassium and IMe4 to 4Np gives [(BIPMTMS)NpIII(I)(IMe4)2] (6Np). The synthesis of 3Np–6Np was facilitated by adopting a scaled-down prechoreographed approach
using cerium synthetic surrogates. The thorium(III) and uranium(III)
analogues of these neptunium(III) complexes are currently unavailable,
meaning that the synthesis of 4Np–6Np provides an example of experimental grounding of 5f- vs 5f- and
5f- vs 4f-element bonding and reactivity comparisons being led by
nonaqueous transuranium chemistry rather than thorium and uranium
congeners. Computational analysis suggests that these NpIII=C bonds are more covalent than UIII=C,
CeIII=C, and PmIII=C congeners
but comparable to analogous UIV=C bonds in terms
of bond orders and total metal contributions to the M=C bonds.
A preliminary assessment of NpIII=C reactivity has
introduced multiple bond metathesis to transuranium chemistry, extending
the range of known metallo-Wittig reactions to encompass actinide
oxidation states III-VI.
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Affiliation(s)
- Conrad A P Goodwin
- Department of Chemistry and Centre for Radiochemistry Research, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.,Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ashley J Wooles
- Department of Chemistry and Centre for Radiochemistry Research, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Jesse Murillo
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Erli Lu
- Department of Chemistry and Centre for Radiochemistry Research, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Josef T Boronski
- Department of Chemistry and Centre for Radiochemistry Research, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Brian L Scott
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Andrew J Gaunt
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Stephen T Liddle
- Department of Chemistry and Centre for Radiochemistry Research, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
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Abstract
Neptunium was the first actinide element to be artificially synthesized, yet, compared with its more famous neighbours uranium and plutonium, is less conspicuously studied. Most neptunium chemistry involves the neptunyl di(oxo)-motif, and transuranic compounds with one metal-ligand multiple bond are rare, being found only in extended-structure oxide, fluoride or oxyhalide materials. These combinations stabilize the required high oxidation states, which are otherwise challenging to realize for transuranic ions. Here we report the synthesis, isolation and characterization of a stable molecular neptunium(V)-mono(oxo) triamidoamine complex. We describe a strong Np≡O triple bond with dominant 5f-orbital contributions and σu > πu energy ordering, akin to terminal uranium-nitrides and di(oxo)-actinyls, but not the uranium-mono(oxo) triple bonds or other actinide multiple bonds reported so far. This work demonstrates that molecular high-oxidation-state transuranic complexes with a single metal-ligand bond can be stabilized and studied in isolation.
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Goodwin CAP, Janicke MT, Scott BL, Gaunt AJ. [AnI 3(THF) 4] (An = Np, Pu) Preparation Bypassing An 0 Metal Precursors: Access to Np 3+/Pu 3+ Nonaqueous and Organometallic Complexes. J Am Chem Soc 2021; 143:20680-20696. [PMID: 34854294 DOI: 10.1021/jacs.1c07967] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Direct comparison of homologous molecules provides a foundation from which to elucidate both subtle and patent changes in reactivity patterns, redox processes, and bonding properties across a series of elements. While trivalent molecular U chemistry is richly developed, analogous Np or Pu research has long been hindered by synthetic routes often requiring scarcely available metallic-phase source material, high-temperature solid-state reactions producing poorly soluble binary halides, or the use of pyrophoric reagents. The development of routes to nonaqueous Np3+/Pu3+ from widely available precursors can potentially transform the scope and pace of research into actinide periodicity. Here, aqueous stocks of An4+ (An = Np, Pu) are dehydrated to well-defined [AnCl4(DME)2] (DME = 1,2-dimethoxyethane), and then a single-step halide exchange/reduction employing Me3SiI produces [AnI3(THF)4] (THF = tetrahydrofuran) in a high to nearly quantitative crystalline yield (with I2 and Me3SiCl as easily removed byproducts). We demonstrate the synthetic utility of these An-iodide molecules, prepared by metal0-free routes, through characterization of archetypal complexes including the tris-silylamide, [Np{N(SiMe3)2}3], and bent metallocenes, [An(C5Me5)2(I)(THF)] (An = Np, Pu)─chosen because both motifs are ubiquitous in Th, U, and lanthanide research. The synthesis of [Np{N(Se═PPh2)2}3] is also reported, completing an isomorphous series that now extends from U to Am and is the first characterized Np3+-Se bond.
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Affiliation(s)
- Conrad A P Goodwin
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Michael T Janicke
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Brian L Scott
- Materials Physics & Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Andrew J Gaunt
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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Staun SL, Wu G, Lukens WW, Hayton TW. Synthesis of a heterobimetallic actinide nitride and an analysis of its bonding. Chem Sci 2021; 12:15519-15527. [PMID: 35003580 PMCID: PMC8653994 DOI: 10.1039/d1sc05072a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 11/13/2021] [Indexed: 11/21/2022] Open
Abstract
Reaction of [K(DME)][Th{N(R)(SiMe2 CH2)}2(NR2)] (R = SiMe3) with 1 equiv. of [U(NR2)3(NH2)] (1) in THF, in the presence of 18-crown-6, results in formation of a bridged uranium-thorium nitride complex, [K(18-crown-6)(THF)2][(NR2)3UIV(μ-N)ThIV(NR2)3] (2), which can be isolated in 48% yield after work-up. Complex 2 is the first isolable molecular mixed-actinide nitride complex. Also formed in the reaction is the methylene-bridged mixed-actinide nitride, [K(18-crown-6)][K(18-crown-6)(Et2O)2][(NR2)2U(μ-N)(μ-κ2-C,N-CH2SiMe2NR)Th(NR2)2]2 (3), which can be isolated in 34% yield after work-up. Complex 3 is likely generated by deprotonation of a methyl group in 2 by [NR2]-, yielding the new μ-CH2 moiety and HNR2. Reaction of 2 with 0.5 equiv. of I2 results in formation of a UV/ThIV bridged nitride, [(NR2)3UV(μ-N)ThIV(NR2)3] (4), which can be isolated in 42% yield after work-up. The electronic structure of 4 was analyzed with EPR spectroscopy, SQUID magnetometry, and NIR-visible spectroscopy. This analysis demonstrated that the energies of 5f orbitals of 4 are largely determined by the strong ligand field exerted by the nitride ligand.
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Affiliation(s)
- Selena L Staun
- Department of Chemistry and Biochemistry, University of California, Santa Barbara Santa Barbara California 93106 USA
| | - Guang Wu
- Department of Chemistry and Biochemistry, University of California, Santa Barbara Santa Barbara California 93106 USA
| | - Wayne W Lukens
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley California 94720 USA
| | - Trevor W Hayton
- Department of Chemistry and Biochemistry, University of California, Santa Barbara Santa Barbara California 93106 USA
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Su J, Cheisson T, McSkimming A, Goodwin CAP, DiMucci IM, Albrecht-Schönzart T, Scott BL, Batista ER, Gaunt AJ, Kozimor SA, Yang P, Schelter EJ. Complexation and redox chemistry of neptunium, plutonium and americium with a hydroxylaminato ligand. Chem Sci 2021; 12:13343-13359. [PMID: 34777753 PMCID: PMC8528073 DOI: 10.1039/d1sc03905a] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/03/2021] [Indexed: 11/25/2022] Open
Abstract
There is significant interest in ligands that can stabilize actinide ions in oxidation states that can be exploited to chemically differentiate 5f and 4f elements. Applications range from developing large-scale actinide separation strategies for nuclear industry processing to carrying out analytical studies that support environmental monitoring and remediation efforts. Here, we report syntheses and characterization of Np(iv), Pu(iv) and Am(iii) complexes with N-tert-butyl-N-(pyridin-2-yl)hydroxylaminato, [2-(tBuNO)py]−(interchangeable hereafter with [(tBuNO)py]−), a ligand which was previously found to impart remarkable stability to cerium in the +4 oxidation state. An[(tBuNO)py]4 (An = Pu, 1; Np, 2) have been synthesized, characterized by X-ray diffraction, X-ray absorption, 1H NMR and UV-vis-NIR spectroscopies, and cyclic voltammetry, along with computational modeling and analysis. In the case of Pu, oxidation of Pu(iii) to Pu(iv) was observed upon complexation with the [(tBuNO)py]− ligand. The Pu complex 1 and Np complex 2 were also isolated directly from Pu(iv) and Np(iv) precursors. Electrochemical measurements indicate that a Pu(iii) species can be accessed upon one-electron reduction of 1 with a large negative reduction potential (E1/2 = −2.26 V vs. Fc+/0). Applying oxidation potentials to 1 and 2 resulted in ligand-centered electron transfer reactions, which is different from the previously reported redox chemistry of UIV[(tBuNO)py]4 that revealed a stable U(v) product. Treatment of an anhydrous Am(iii) precursor with the [(tBuNO)py]− ligand did not result in oxidation to Am(iv). Instead, the dimeric complex [AmIII(μ2-(tBuNO)py)((tBuNO)py)2]2 (3) was isolated. Complex 3 is a rare example of a structurally characterized non-aqueous Am-containing molecular complex prepared using inert atmosphere techniques. Predicted redox potentials from density functional theory calculations show a trivalent accessibility trend of U(iii) < Np(iii) < Pu(iii) and that the higher oxidation states of actinides (i.e., +5 for Np and Pu and +4 for Am) are not stabilized by [2-(tBuNO)py]−, in good agreement with experimental observations. The coordination modes and electronic properties of a strongly coordinating hydroxylaminato ligand with Np, Pu and Am were investigated.Complexes were characterized by a range of experimental and computational techniques.![]()
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Affiliation(s)
- Jing Su
- Theoretical Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Thibault Cheisson
- P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S 34th St. Philadelphia Pennsylvania 19104 USA
| | - Alex McSkimming
- P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S 34th St. Philadelphia Pennsylvania 19104 USA
| | - Conrad A P Goodwin
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Ida M DiMucci
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Thomas Albrecht-Schönzart
- Department of Chemistry and Biochemistry, Florida State University 95 Chieftan Way Tallahassee Florida 32306 USA
| | - Brian L Scott
- Materials and Physics Applications Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Enrique R Batista
- Theoretical Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Andrew J Gaunt
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Stosh A Kozimor
- Chemistry Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Ping Yang
- Theoretical Division, Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | - Eric J Schelter
- P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S 34th St. Philadelphia Pennsylvania 19104 USA
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