23 results on '"Enrique R Batista"'
Search Results
2. Advancing Chelation Chemistry for Actinium and Other +3 f-Elements, Am, Cm, and La
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Eva R. Birnbaum, Stosh A. Kozimor, Brian L. Scott, Veronika Mocko, Samantha K. Cary, Ping Yang, Kevin D. John, Amanda Morgenstern, Benjamin W. Stein, Maryline G. Ferrier, Enrique R. Batista, Sharon E. Bone, and Juan S. Lezama Pacheco
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Actinium ,Inorganic chemistry ,Binding pocket ,chemistry.chemical_element ,010402 general chemistry ,Ligands ,01 natural sciences ,Biochemistry ,Catalysis ,Coordination complex ,Colloid and Surface Chemistry ,Organophosphorus Compounds ,Coordination Complexes ,Lanthanum ,Molecule ,Chelation ,Chelating Agents ,chemistry.chemical_classification ,Americium ,Extended X-ray absorption fine structure ,Molecular Structure ,Extramural ,General Chemistry ,0104 chemical sciences ,chemistry ,Curium ,Radiopharmaceuticals - Abstract
A major chemical challenge facing implementation of 225Ac in targeted alpha therapy-an emerging technology that has potential for treatment of disease-is identifying an 225Ac chelator that is compatible with in vivo applications. It is unclear how to tailor a chelator for Ac binding because Ac coordination chemistry is poorly defined. Most Ac chemistry is inferred from radiochemical experiments carried out on microscopic scales. Of the few Ac compounds that have been characterized spectroscopically, success has only been reported for simple inorganic ligands. Toward advancing understanding in Ac chelation chemistry, we have developed a method for characterizing Ac complexes that contain highly complex chelating agents using small quantities (μg) of 227Ac. We successfully characterized the chelation of Ac3+ by DOTP8- using EXAFS, NMR, and DFT techniques. To develop confidence and credibility in the Ac results, comparisons with +3 cations (Am, Cm, and La) that could be handled on the mg scale were carried out. We discovered that all M3+ cations (M = Ac, Am, Cm, La) were completely encapsulated within the binding pocket of the DOTP8- macrocycle. The computational results highlighted the stability of the M(DOTP)5- complexes.
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- 2019
3. Identification of the Formal +2 Oxidation State of Neptunium: Synthesis and Structural Characterization of {NpII[C5H3(SiMe3)2]3}1–
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Andrew J. Gaunt, David H. Woen, Stosh A. Kozimor, Michael T. Janicke, Brian L. Scott, William J. Evans, Cory J. Windorff, Jing Su, Enrique R. Batista, and Ping Yang
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010405 organic chemistry ,Chemistry ,Neptunium ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Characterization (materials science) ,Ion ,Crystallography ,Colloid and Surface Chemistry ,Oxidation state ,Density functional theory ,Electron configuration ,Ground state - Abstract
We report a new formal oxidation state for neptunium in a crystallographically characterizable molecular complex, namely Np2+ in [K(crypt)][NpIICp″3] [crypt = 2.2.2-cryptand, Cp″ = C5H3(SiMe3)2]. Density functional theory calculations indicate that the ground state electronic configuration of the Np2+ ion in the complex is 5f46d1.
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- 2018
4. Quantitative Evidence for Lanthanide-Oxygen Orbital Mixing in CeO2, PrO2, and TbO2
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Enrique R. Batista, S. Chantal E. Stieber, David Clark, Richard L. Martin, Stefan G. Minasian, Stosh A. Kozimor, Jason M. Keith, David K. Shuh, Xiaodong Wen, Wayne W. Lukens, Corwin H. Booth, and Tolek Tylisczcak
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Lanthanide ,X-ray absorption spectroscopy ,Absorption spectroscopy ,Chemistry ,Ionic bonding ,02 engineering and technology ,General Chemistry ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Atomic orbital ,Covalent bond ,Physical chemistry ,Density functional theory ,0210 nano-technology - Abstract
© 2017 American Chemical Society. Understanding the nature of covalent (band-like) vs ionic (atomic-like) electrons in metal oxides continues to be at the forefront of research in the physical sciences. In particular, the development of a coherent and quantitative model of bonding and electronic structure for the lanthanide dioxides, LnO2(Ln = Ce, Pr, and Tb), has remained a considerable challenge for both experiment and theory. Herein, relative changes in mixing between the O 2p orbitals and the Ln 4f and 5d orbitals in LnO2are evaluated quantitatively using O K-edge X-ray absorption spectroscopy (XAS) obtained with a scanning transmission X-ray microscope and density functional theory (DFT) calculations. For each LnO2, the results reveal significant amounts of Ln 5d and O 2p mixing in the orbitals of t2g(σ-bonding) and eg(π-bonding) symmetry. The remarkable agreement between experiment and theory also shows that significant mixing with the O 2p orbitals occurs in a band derived from the 4f orbitals of a2usymmetry (σ-bonding) for each compound. However, a large increase in orbital mixing is observed for PrO2that is ascribed to a unique interaction derived from the 4f orbitals of t1usymmetry (σ- and π-bonding). O K-edge XAS and DFT results are compared with complementary L3-edge and M5,4-edge XAS measurements and configuration interaction calculations, which shows that each spectroscopic approach provides evidence for ground state O 2p and Ln 4f orbital mixing despite inducing very different core-hole potentials in the final state.
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- 2017
5. Covalency in Americium(III) Hexachloride
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Stosh A. Kozimor, Justin N. Cross, Brian L. Scott, Samantha K. Cary, Ping Yang, Enrique R. Batista, Cory J. Windorff, Benjamin W. Stein, William J. Evans, Jing Su, and Veronika Mocko
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X-ray absorption spectroscopy ,Americium ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Extramural ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Chlorides ,Chemical physics ,Computational chemistry ,Mixing (physics) - Abstract
Developing a better understanding of covalency (or orbital mixing) is of fundamental importance. Covalency occupies a central role in directing chemical and physical properties for almost any given compound or material. Hence, the concept of covalency has potential to generate broad and substantial scientific advances, ranging from biological applications to condensed matter physics. Given the importance of orbital mixing combined with the difficultly in measuring covalency, estimating or inferring covalency often leads to fiery debate. Consider the 60-year controversy sparked by Seaborg and co-workers ( Diamond, R. M.; Street, K., Jr.; Seaborg, G. T. J. Am. Chem. Soc. 1954 , 76 , 1461 ) when it was proposed that covalency from 5f-orbitals contributed to the unique behavior of americium in chloride matrixes. Herein, we describe the use of ligand K-edge X-ray absorption spectroscopy (XAS) and electronic structure calculations to quantify the extent of covalent bonding in-arguably-one of the most difficult systems to study, the Am-Cl interaction within AmCl
- Published
- 2017
6. Energy-Degeneracy-Driven Covalency in Actinide Bonding
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Andrew Kerridge, Steven D. Conradson, Sharon E. Bone, Alex S. Ditter, Samantha K. Cary, Marianne P. Wilkerson, Enrique R. Batista, Richard L. Martin, Stefan G. Minasian, Stosh A. Kozimor, Henry S. La Pierre, Nikolas Kaltsoyannis, Kevin S. Boland, Matthias W. Löble, Veronika Mocko, Jason M. Keith, Laura E. Wolfsberg, David K. Shuh, David Clark, J. A. Bradley, Jing Su, Gerald T. Seidler, and Ping Yang
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Chemical substance ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Actinide ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Metal ,ResearchInstitutes_Networks_Beacons/dalton_nuclear_institute ,Colloid and Surface Chemistry ,Chemical bond ,Covalent bond ,visual_art ,Chemical Sciences ,visual_art.visual_art_medium ,Physical chemistry ,Dalton Nuclear Institute ,Density functional theory ,Degeneracy (biology) - Abstract
Evaluating the nature of chemical bonding for actinide elements represents one of the most important and long-standing problems in actinide science. We directly address this challenge and contribute a Cl K-edge X-ray absorption spectroscopy and relativistic density functional theory study that quantitatively evaluates An-Cl covalency in AnCl62- (AnIV = Th, U, Np, Pu). The results showed significant mixing between Cl 3p- and AnIV 5f- and 6d-orbitals (t1u*/t2u* and t2 g*/eg *), with the 6d-orbitals showing more pronounced covalent bonding than the 5f-orbitals. Moving from Th to U, Np, and Pu markedly changed the amount of M-Cl orbital mixing, such that AnIV 6d - and Cl 3p-mixing decreased and metal 5f - and Cl 3p-orbital mixing increased across this series.
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- 2018
7. Identification of the Formal +2 Oxidation State of Neptunium: Synthesis and Structural Characterization of {Np
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Jing, Su, Cory J, Windorff, Enrique R, Batista, William J, Evans, Andrew J, Gaunt, Michael T, Janicke, Stosh A, Kozimor, Brian L, Scott, David H, Woen, and Ping, Yang
- Abstract
We report a new formal oxidation state for neptunium in a crystallographically characterizable molecular complex, namely Np
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- 2018
8. Quantitative Evidence for Lanthanide-Oxygen Orbital Mixing in CeO
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Stefan G, Minasian, Enrique R, Batista, Corwin H, Booth, David L, Clark, Jason M, Keith, Stosh A, Kozimor, Wayne W, Lukens, Richard L, Martin, David K, Shuh, S Chantal E, Stieber, Tolek, Tylisczcak, and Xiao-Dong, Wen
- Abstract
Understanding the nature of covalent (band-like) vs ionic (atomic-like) electrons in metal oxides continues to be at the forefront of research in the physical sciences. In particular, the development of a coherent and quantitative model of bonding and electronic structure for the lanthanide dioxides, LnO
- Published
- 2017
9. Covalency in Lanthanides. An X-ray Absorption Spectroscopy and Density Functional Theory Study of LnCl6x– (x = 3, 2)
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Kevin S. Boland, Matthias W. Löble, Brian L. Scott, Alison B. Altman, Marianne P. Wilkerson, David Clark, Angela C. Olson, Ralph A. Zehnder, Steven D. Conradson, David K. Shuh, Stosh A. Kozimor, Juan S. Lezama Pacheco, Tolek Tyliszczak, Richard L. Martin, Stefan G. Minasian, Enrique R. Batista, S. Chantal E. Stieber, and Jason M. Keith
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Lanthanide ,X-ray absorption spectroscopy ,Absorption spectroscopy ,Chemistry ,Inorganic chemistry ,General Chemistry ,Time-dependent density functional theory ,Configuration interaction ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,Oxidation state ,Covalent bond ,Physical chemistry ,Density functional theory - Abstract
Covalency in Ln-Cl bonds of Oh-LnCl6(x-) (x = 3 for Ln = Ce(III), Nd(III), Sm(III), Eu(III), Gd(III); x = 2 for Ln = Ce(IV)) anions has been investigated, primarily using Cl K-edge X-ray absorption spectroscopy (XAS) and time-dependent density functional theory (TDDFT); however, Ce L3,2-edge and M5,4-edge XAS were also used to characterize CeCl6(x-) (x = 2, 3). The M5,4-edge XAS spectra were modeled using configuration interaction calculations. The results were evaluated as a function of (1) the lanthanide (Ln) metal identity, which was varied across the series from Ce to Gd, and (2) the Ln oxidation state (when practical, i.e., formally Ce(III) and Ce(IV)). Pronounced mixing between the Cl 3p- and Ln 5d-orbitals (t2g* and eg*) was observed. Experimental results indicated that Ln 5d-orbital mixing decreased when moving across the lanthanide series. In contrast, oxidizing Ce(III) to Ce(IV) had little effect on Cl 3p and Ce 5d-orbital mixing. For LnCl6(3-) (formally Ln(III)), the 4f-orbitals participated only marginally in covalent bonding, which was consistent with historical descriptions. Surprisingly, there was a marked increase in Cl 3p- and Ce(IV) 4f-orbital mixing (t1u* + t2u*) in CeCl6(2-). This unexpected 4f- and 5d-orbital participation in covalent bonding is presented in the context of recent studies on both tetravalent transition metal and actinide hexahalides, MCl6(2-) (M = Ti, Zr, Hf, U).
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- 2015
10. On the Origin of Covalent Bonding in Heavy Actinides
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Matthew Urban, Enrique R. Batista, Jing Su, Ping Yang, Morgan Luckey, Morgan P. Kelley, and Jenifer C. Shafer
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010405 organic chemistry ,Chemistry ,Ligand ,Nuclear Theory ,Ionic bonding ,General Chemistry ,Orbital overlap ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Specific orbital energy ,Colloid and Surface Chemistry ,Atomic orbital ,Chemical physics ,Covalent bond ,Condensed Matter::Strongly Correlated Electrons ,Molecular orbital ,Degeneracy (biology) ,Atomic physics ,Nuclear Experiment - Abstract
Recent reports have suggested the late actinides participate in more covalent interactions than the earlier actinides, yet the origin of this shift in chemistry is not understood. This report considers the chemistry of actinide dipicolinate complexes to identify why covalent interactions become more prominent for heavy actinides. A modest increase in measured actinide:dipicolinate stability constants is coincident with a significant increase in An 5f energy degeneracy with the dipicolinate molecular orbitals for Bk and Cf relative to Am and Cm. While the interactions in the actinide-dipicolinate complex are largely ionic, the decrease in 5f orbital energy across the series manifests in orbital-mixing and, hence, covalency driven by energy degeneracy. This observation suggests the origin of covalency in heavy actinide interactions stems from the degeneracy of 5f orbitals with ligand molecular orbitals rather than spatial orbital overlap. These findings suggest that the limiting radial extension of the 5f orbitals later in the actinide series could make the heavy actinides ideal elements to probe and tune effects of energy degeneracy driven covalency.
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- 2017
11. Tetrahalide Complexes of the [U(NR)2]2+ Ion: Synthesis, Theory, and Chlorine K-Edge X-ray Absorption Spectroscopy
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Trevor W. Hayton, Marianne P. Wilkerson, Kevin S. Boland, Brian L. Scott, Richard L. Martin, Stefan G. Minasian, Ping Yang, David K. Shuh, Robert E. Jilek, Steven D. Conradson, James M. Boncella, Molly M. MacInnes, David Clark, Enrique R. Batista, Stosh A. Kozimor, Angela C. Olson, and Liam P. Spencer
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Models, Molecular ,X-ray absorption spectroscopy ,Absorption spectroscopy ,Chemistry ,Inorganic chemistry ,Halide ,General Chemistry ,Electronic structure ,Time-dependent density functional theory ,Imides ,Biochemistry ,Catalysis ,Ion ,Crystallography ,X-Ray Absorption Spectroscopy ,Colloid and Surface Chemistry ,K-edge ,Organometallic Compounds ,Quantum Theory ,Uranium ,Density functional theory ,Chlorine - Abstract
Synthetic routes to salts containing uranium bis-imido tetrahalide anions [U(NR)(2)X(4)](2-) (X = Cl(-), Br(-)) and non-coordinating NEt(4)(+) and PPh(4)(+) countercations are reported. In general, these compounds can be prepared from U(NR)(2)I(2)(THF)(x) (x = 2 and R = (t)Bu, Ph; x = 3 and R = Me) upon addition of excess halide. In addition to providing stable coordination complexes with Cl(-), the [U(NMe)(2)](2+) cation also reacts with Br(-) to form stable [NEt(4)](2)[U(NMe)(2)Br(4)] complexes. These materials were used as a platform to compare electronic structure and bonding in [U(NR)(2)](2+) with [UO(2)](2+). Specifically, Cl K-edge X-ray absorption spectroscopy (XAS) and both ground-state and time-dependent hybrid density functional theory (DFT and TDDFT) were used to probe U-Cl bonding interactions in [PPh(4)](2)[U(N(t)Bu)(2)Cl(4)] and [PPh(4)](2)[UO(2)Cl(4)]. The DFT and XAS results show the total amount of Cl 3p character mixed with the U 5f orbitals was roughly 7-10% per U-Cl bond for both compounds, which shows that moving from oxo to imido has little effect on orbital mixing between the U 5f and equatorial Cl 3p orbitals. The results are presented in the context of recent Cl K-edge XAS and DFT studies on other hexavalent uranium chloride systems with fewer oxo or imido ligands.
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- 2013
12. Sulfur K-edge X-ray Absorption Spectroscopy and Time-Dependent Density Functional Theory of Dithiophosphinate Extractants: Minor Actinide Selectivity and Electronic Structure Correlations
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David Clark, Scott R. Daly, Jason M. Keith, Kevin S. Boland, Stosh A. Kozimor, Richard L. Martin, and Enrique R. Batista
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Lanthanide ,X-ray absorption spectroscopy ,Absorption spectroscopy ,ved/biology ,Chemistry ,ved/biology.organism_classification_rank.species ,Inorganic chemistry ,General Chemistry ,Time-dependent density functional theory ,Biochemistry ,Catalysis ,Spectral line ,Colloid and Surface Chemistry ,K-edge ,Physical chemistry ,Density functional theory ,Conjugate acid - Abstract
The dithiophosphinic acid HS(2)P(o-CF(3)C(6)H(4))(2) is known to exhibit exceptionally high extraction selectivities for trivalent minor actinides (Am and Cm) in the presence of trivalent lanthanides. To generate insight that may account for this observation, a series of [PPh(4)][S(2)PR(2)] complexes, where R = Me (1), Ph (2), p-CF(3)C(6)H(4) (3), m-CF(3)C(6)H(4) (4), o-CF(3)C(6)H(4) (5), o-MeC(6)H(4) (6), and o-MeOC(6)H(4) (7), have been investigated using sulfur K-edge X-ray absorption spectroscopy (XAS) and time-dependent density functional theory (TDDFT). The experimental analyses show distinct features in the spectrum of S(2)P(o-CF(3)C(6)H(4))(2)(-) (5) that are not present in the spectrum of 4, whose conjugate acid exhibits reduced selectivity, or in the spectra of 2 and 3, which are anticipated to have even lower separation factors based on previous studies. In contrast, the spectrum of 5 is similar to those of 6 and 7, despite the significantly different electron-donating properties associated with the o-CF(3), o-Me, and o-OMe substituents. The TDDFT calculations suggest that the distinct spectral features of 5-7 result from steric interactions due to the presence of the ortho substituents, which force the aryl groups to rotate around the P-C bonds and reduce the molecular symmetry from approximately C(2v) in 2-4 to C(2) in 5-7. As a consequence, the change in aryl group orientation appears to make the ortho-substituted S(2)PR(2)(-) anions "softer" extractants compared with analogous Ph-, p-CF(3)C(6)H(4)-, and m-CF(3)C(6)H(4)-containing ligands (2-4) by raising the energies of the sulfur valence orbitals and enhancing orbital mixing between the S(2)P molecular orbitals and the aryl groups bound to phosphorus. Overall, we report that sulfur K-edge XAS experiments and TDDFT calculations reveal unique electronic properties of the S(2)P(o-CF(3)C(6)H(4))(2)(-) anion in 5. These results correlate with the special extraction properties associated with HS(2)P(o-CF(3)C(6)H(4))(2), and suggest that ligand K-edge XAS and TDDFT can be used to guide separation efforts relevant to advanced fuel cycle development.
- Published
- 2012
13. A Linear trans-Bis(imido) Neptunium(V) Actinyl Analog: Np(V)(NDipp)2((t)Bu2bipy)2Cl (Dipp = 2,6-(i)Pr2C6H3)
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Neil C. Tomson, Jessie L. Brown, James M. Boncella, Brian L. Scott, Enrique R. Batista, Sean D. Reilly, and Andrew J. Gaunt
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Neptunium ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,Uranium ,Biochemistry ,Catalysis ,Bipyridine ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Reagent ,Proton NMR ,Transuranium element - Abstract
The discovery that imido analogs of actinyl dioxo cations can be extended beyond uranium into the transuranic elements is presented. Synthesis of the Np(V) complex, Np(NDipp)2((t)Bu2bipy)2Cl (1), is achieved through treatment of a Np(IV) precursor with a bipyridine coligand and lithium-amide reagent. Complex 1 has been structurally characterized, analyzed by (1)H NMR and UV-vis-NIR spectroscopies, and the electronic structure evaluated by DFT calculations.
- Published
- 2015
14. Carbon K-edge X-ray absorption spectroscopy and time-dependent density functional theory examination of metal-carbon bonding in metallocene dichlorides
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Tolek Tyliszczak, Kevin S. Boland, Jason M. Keith, Louis J. Vernon, Enrique R. Batista, David K. Shuh, Richard L. Martin, Stefan G. Minasian, and Stosh A. Kozimor
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X-ray absorption spectroscopy ,Absorption spectroscopy ,Chemistry ,Analytical chemistry ,chemistry.chemical_element ,General Chemistry ,Time-dependent density functional theory ,Antibonding molecular orbital ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,Atomic orbital ,K-edge ,Density functional theory ,Carbon - Abstract
Metal-carbon covalence in (C5H5)2MCl2 (M = Ti, Zr, Hf) has been evaluated using carbon K-edge X-ray absorption spectroscopy (XAS) as well as ground-state and time-dependent hybrid density functional theory (DFT and TDDFT). Differences in orbital mixing were determined experimentally using transmission XAS of thin crystalline material with a scanning transmission X-ray microscope (STXM). Moving down the periodic table (Ti to Hf) has a marked effect on the experimental transition intensities associated with the low-lying antibonding 1a1* and 1b2* orbitals. The peak intensities, which are directly related to the M-(C5H5) orbital mixing coefficients, increase from 0.08(1) and 0.26(3) for (C5H5)2TiCl2 to 0.31(3) and 0.75(8) for (C5H5)2ZrCl2, and finally to 0.54(5) and 0.83(8) for (C5H5)2HfCl2. The experimental trend toward increased peak intensity for transitions associated with 1a1* and 1b2* orbitals agrees with the calculated TDDFT oscillator strengths [0.10 and 0.21, (C5H5)2TiCl2; 0.21 and 0.73, (C5H5)2ZrCl2; 0.35 and 0.69, (C5H5)2HfCl2] and with the amount of C 2p character obtained from the Mulliken populations for the antibonding 1a1* and 1b2* orbitals [8.2 and 23.4%, (C5H5)2TiCl2; 15.3 and 39.7%, (C5H5)2ZrCl2; 20.1 and 50.9%, (C5H5)2HfCl2]. The excellent agreement between experiment, theory, and recent Cl K-edge XAS and DFT measurements shows that C 2p orbital mixing is enhanced for the diffuse Hf (5d) and Zr (4d) atomic orbitals in relation to the more localized Ti (3d) orbitals. These results provide insight into how changes in M-Cl orbital mixing within the metallocene wedge are correlated with periodic trends in covalent bonding between the metal and the cyclopentadienide ancillary ligands.
- Published
- 2013
15. Covalency in metal-oxygen multiple bonds evaluated using oxygen K-edge spectroscopy and electronic structure theory
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J. A. Bradley, David K. Shuh, Enrique R. Batista, Jason M. Keith, Stosh A. Kozimor, Ping Yang, Gregory L. Wagner, Tsu-Chein Weng, Richard L. Martin, Stefan G. Minasian, Dimosthenis Sokaras, Scott R. Daly, Wayne W. Lukens, Dennis Nordlund, Gerald T. Seidler, Tolek Tyliszczak, and Kevin S. Boland
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Microscopy, Electron, Scanning Transmission ,Absorption spectroscopy ,Molecular Structure ,Chemistry ,X-Rays ,Electrons ,General Chemistry ,Biochemistry ,Catalysis ,XANES ,Specific orbital energy ,Oxygen ,Colloid and Surface Chemistry ,X-Ray Absorption Spectroscopy ,Transition metal ,Atomic orbital ,K-edge ,Metals, Heavy ,Physical chemistry ,Quantum Theory ,Density functional theory ,Spectroscopy - Abstract
Advancing theories of how metal-oxygen bonding influences metal oxo properties can expose new avenues for innovation in materials science, catalysis, and biochemistry. Historically, spectroscopic analyses of the transition metal MO(4)(x-) anions have formed the basis for new M-O bonding theories. Herein, relative changes in M-O orbital mixing in MO(4)(2-) (M = Cr, Mo, W) and MO(4)(-) (M = Mn, Tc, Re) are evaluated for the first time by nonresonant inelastic X-ray scattering, X-ray absorption spectroscopy using fluorescence and transmission (via a scanning transmission X-ray microscope), and time-dependent density functional theory. The results suggest that moving from Group 6 to Group 7 or down the triads increases M-O e* (π*) mixing; for example, it more than doubles in ReO(4)(-) relative to CrO(4)(2-). Mixing in the t(2)* orbitals (σ* + π*) remains relatively constant within the same Group, but increases on moving from Group 6 to Group 7. These unexpected changes in orbital energy and composition for formally isoelectronic tetraoxometalates are evaluated in terms of periodic trends in d orbital energy and radial extension.
- Published
- 2013
16. Scanning tunneling microscopy and theoretical study of water adsorption on Fe3O4: implications for catalysis
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Daejin Eom, Maria Flytzani-Stephanopoulos, Xiaodong Wen, Kwang Taeg Rim, Siu-Wai Chan, George W. Flynn, and Enrique R. Batista
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chemistry.chemical_element ,General Chemistry ,Hematite ,Biochemistry ,Oxygen ,Catalysis ,Dissociation (chemistry) ,law.invention ,Crystallography ,Colloid and Surface Chemistry ,Adsorption ,chemistry ,Computational chemistry ,law ,visual_art ,visual_art.visual_art_medium ,Molecule ,Scanning tunneling microscope ,Single crystal - Abstract
The reduced surface of a natural Hematite single crystal α-Fe(2)O(3)(0001) sample has multiple surface domains with different terminations, Fe(2)O(3)(0001), FeO(111), and Fe(3)O(4)(111). The adsorption of water on this surface was investigated via Scanning Tunneling Microscopy (STM) and first-principle theoretical simulations. Water species are observed only on the Fe-terminated Fe(3)O(4)(111) surface at temperatures up to 235 K. Between 235 and 245 K we observed a change in the surface species from intact water molecules and hydroxyl groups bound to the surface to only hydroxyl groups atop the surface terminating Fe(III) cations. This indicates a low energy barrier for water dissociation on the surface of Fe(3)O(4) that is supported by our theoretical computations. Our first principles simulations confirm the identity of the surface species proposed from the STM images, finding that the most stable state of a water molecule is the dissociated one (OH + H), with OH atop surface terminating Fe(III) sites and H atop under-coordinated oxygen sites. Attempts to simulate reaction of the surface OH with coadsorbed CO fail because the only binding sites for CO are the surface Fe(III) atoms, which are blocked by the much more strongly bound OH. In order to promote this reaction we simulated a surface decorated with gold atoms. The Au adatoms are found to cap the under-coordinated oxygen sites and dosed CO is found to bind to the Au adatom. This newly created binding site for CO not only allows for coexistence of CO and OH on the surface of Fe(3)O(4) but also provides colocation between the two species. These two factors are likely promoters of catalytic activity on Au/Fe(3)O(4)(111) surfaces.
- Published
- 2012
17. Determining relative f and d orbital contributions to M-Cl covalency in MCl6(2-) (M = Ti, Zr, Hf, U) and UOCl5(-) using Cl K-edge X-ray absorption spectroscopy and time-dependent density functional theory
- Author
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Kevin S. Boland, Richard L. Martin, Stefan G. Minasian, Stosh A. Kozimor, Gregory L. Wagner, Marianne P. Wilkerson, Jason M. Keith, Daniel E. Schwarz, Laura E. Wolfsberg, Enrique R. Batista, Ping Yang, David K. Shuh, Steven D. Conradson, and David Clark
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X-ray absorption spectroscopy ,Valence (chemistry) ,Absorption spectroscopy ,Chemistry ,General Chemistry ,Electronic structure ,Time-dependent density functional theory ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,K-edge ,Atomic orbital ,Physical chemistry ,Density functional theory ,Atomic physics - Abstract
Chlorine K-edge X-ray absorption spectroscopy (XAS) and ground-state and time-dependent hybrid density functional theory (DFT) were used to probe the electronic structures of O(h)-MCl(6)(2-) (M = Ti, Zr, Hf, U) and C(4v)-UOCl(5)(-), and to determine the relative contributions of valence 3d, 4d, 5d, 6d, and 5f orbitals in M-Cl bonding. Spectral interpretations were guided by time-dependent DFT calculated transition energies and oscillator strengths, which agree well with the experimental XAS spectra. The data provide new spectroscopic evidence for the involvement of both 5f and 6d orbitals in actinide-ligand bonding in UCl(6)(2-). For the MCl(6)(2-), where transitions into d orbitals of t(2g) symmetry are spectroscopically resolved for all four complexes, the experimentally determined Cl 3p character per M-Cl bond increases from 8.3(4)% (TiCl(6)(2-)) to 10.3(5)% (ZrCl(6)(2-)), 12(1)% (HfCl(6)(2-)), and 18(1)% (UCl(6)(2-)). Chlorine K-edge XAS spectra of UOCl(5)(-) provide additional insights into the transition assignments by lowering the symmetry to C(4v), where five pre-edge transitions into both 5f and 6d orbitals are observed. For UCl(6)(2-), the XAS data suggest that orbital mixing associated with the U 5f orbitals is considerably lower than that of the U 6d orbitals. For both UCl(6)(2-) and UOCl(5)(-), the ground-state DFT calculations predict a larger 5f contribution to bonding than is determined experimentally. These findings are discussed in the context of conventional theories of covalent bonding for d- and f-block metal complexes.
- Published
- 2012
18. Experimental and theoretical comparison of the O K-edge nonresonant inelastic X-ray scattering and X-ray absorption spectra of NaReO4
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David Clark, J. A. Bradley, Richard L. Martin, Laura E. Wolfsberg, Kevin S. Boland, Stosh A. Kozimor, Brian L. Scott, Steven D. Conradson, Carol J. Burns, Enrique R. Batista, Ping Yang, David K. Shuh, Tolek Tyliszczak, Marianne P. Wilkerson, and Gerald T. Seidler
- Subjects
X-ray absorption spectroscopy ,Absorption spectroscopy ,Scattering ,Chemistry ,X-ray ,Analytical chemistry ,General Chemistry ,Biochemistry ,Catalysis ,Spectral line ,Colloid and Surface Chemistry ,K-edge ,Microscopy ,Saturation (chemistry) - Abstract
Accurate X-ray absorption spectra (XAS) of first row atoms, e.g., O, are notoriously difficult to obtain due to the extreme sensitivity of the measurement to surface contamination, self-absorption, and saturation affects. Herein, we describe a comprehensive approach for determining reliable O K-edge XAS data for ReO(4)(1-) and provide methodology for obtaining trustworthy and quantitative data on nonconducting molecular systems, even in the presence of surface contamination. This involves comparing spectra measured by nonresonant inelastic X-ray scattering (NRIXS), a bulk-sensitive technique that is not prone to X-ray self-absorption and provides exact peak intensities, with XAS spectra obtained by three different detection modes, namely total electron yield (TEY), fluorescence yield (FY), and scanning transmission X-ray microscopy (STXM). For ReO(4)(1-), TEY measurements were heavily influenced by surface contamination, while the FY and STXM data agree well with the bulk NRIXS analysis. These spectra all showed two intense pre-edge features indicative of the covalent interaction between the Re 5d and O 2p orbitals. Density functional theory calculations were used to assign these two peaks as O 1s excitations to the e and t(2) molecular orbitals that result from Re 5d and O 2p covalent mixing in T(d) symmetry. Electronic structure calculations were used to determine the amount of O 2p character (%) in these molecular orbitals. Time dependent-density functional theory (TD-DFT) was also used to calculate the energies and intensities of the pre-edge transitions. Overall, under these experimental conditions, this analysis suggests that NRIXS, STXM, and FY operate cooperatively, providing a sound basis for validation of bulk-like excitation spectra and, in combination with electronic structure calculations, suggest that NaReO(4) may serve as a well-defined O K-edge energy and intensity standard for future O K-edge XAS studies.
- Published
- 2010
19. Trends in covalency for d- and f-element metallocene dichlorides identified using chlorine K-edge X-ray absorption spectroscopy and time-dependent density functional theory
- Author
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Laura E. Wolfsberg, Steven D. Conradson, Richard L. Martin, Stosh A. Kozimor, Enrique R. Batista, Kevin S. Boland, Carol J. Burns, Ping Yang, Marianne P. Wilkerson, and David Clark
- Subjects
X-ray absorption spectroscopy ,Absorption spectroscopy ,Chemistry ,Inorganic chemistry ,General Chemistry ,Electronic structure ,Time-dependent density functional theory ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,K-edge ,Atomic orbital ,Principal quantum number ,Physical chemistry ,Density functional theory - Abstract
We describe the use of Cl K-edge X-ray absorption spectroscopy (XAS) and both ground-state and time-dependent hybrid density functional theory (DFT) to probe the electronic structure and determine the degree of orbital mixing in M-Cl bonds for (C(5)Me(5))(2)MCl(2) (M = Ti, 1; Zr, 2; Hf, 3; Th, 4; U, 5), where we can directly compare a class of structurally similar compounds for d- and f-elements. Pre-edge features in the Cl K-edge XAS data for the group IV transition-metals 1-3 provide direct evidence of covalent M-Cl orbital mixing. The amount of Cl 3p character was experimentally determined to be 25%, 23%, and 22% per M-Cl bond for 1-3, respectively. For actinides, we find a pre-edge shoulder for 4 (Th) and distinct and weak pre-edge features for U, 5. The amount of Cl 3p character was determined to be 9% for 5, and we were unable to make an experimental determination for 4. Using hybrid DFT calculations with relativistic effective core potentials, the electronic structures of 1-5 were calculated and used as a guide to interpret the experimental Cl K-edge XAS data. For transition-metal compounds 1-3, the pre-edge features arise due to transitions from Cl 1s electrons into the 3d-, 4d-, and 5d-orbitals, with assignments provided in the text. For Th, 4, we find that 5f- and 6d-orbitals are nearly degenerate and give rise to a single pre-edge shoulder in the XAS. For U, 5, we find the 5f- and 6d-orbitals fall into two distinct energy groupings, and Cl K-edge XAS data are interpreted in terms of Cl 1s transitions into both 5f- and 6d-orbitals. Time-dependent DFT was used to calculate the energies and intensities of Cl 1s transitions into empty metal-based orbitals containing Cl 3p character and provide simulated Cl K-edge XAS spectra for 1-4. For 5, which has two unpaired 5f electrons, simulated spectra were obtained from transition dipole calculations using ground-state Kohn-Sham orbitals. To the best of our knowledge, this represents the first application of Cl K-edge XAS to actinide systems. Overall, this study allows trends in orbital mixing within a well-characterized structural motif to be identified and compared between transition-metals and actinide elements. These results show that the orbital mixing for the d-block compounds slightly decreases in covalency with increasing principal quantum number, in the order Ti > Zr approximately = Hf, and that uranium displays approximately half the covalent orbital mixing of transition elements.
- Published
- 2009
20. Imido exchange in bis(imido) uranium(VI) complexes with aryl isocyanates
- Author
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James M. Boncella, Liam P. Spencer, Brian L. Scott, Enrique R. Batista, and Ping Yang
- Subjects
Chemistry ,Ligand ,Aryl ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Actinide ,Uranium ,Biochemistry ,Medicinal chemistry ,Isocyanate ,Catalysis ,Cycloaddition ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Transition metal ,Density functional theory - Abstract
Addition of 1 and 2 equiv of ArNCO (ArPh, 2,4,6-Me3C6H2) to U(NtBu)2(I)2(OPPh3)2 yields the aryl−imido complexes U(NAr)(NtBu)(I)2(OPPh3)2 and U(NAr)2(I)2(OPPh3)2, respectively. Unlike analogous transition metal reactions this imido exchange reaction does not proceed through a metal oxo intermediate. Density functional theory calculations and 15N-labeling studies suggest this transformation involves the [2 + 2] cycloaddition of the aryl isocyanate CN bond across the UN imido ligand to form an N,N-bound ureato intermediate.
- Published
- 2008
21. Exchange of an imido ligand in bis(imido) complexes of uranium
- Author
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Trevor W. Hayton, Enrique R. Batista, James M. Boncella, and Brian L. Scott
- Subjects
Colloid and Surface Chemistry ,chemistry ,Ligand ,Stereochemistry ,chemistry.chemical_element ,General Chemistry ,Uranium ,Biochemistry ,Medicinal chemistry ,Catalysis ,Adduct - Abstract
Addition of B(C6H5)3.H2O to U(NtBu)2I2(THF)2 provides U(NtBu)(O)I2(THF)2, a complex with a trans arrangement of the oxo and imido ligands. A DFT study on the Ph3PO adduct, U(NtBu)(O)I2(Ph3PO)2, reveals that there are six bonding orbitals in the O=U=N interaction, much like the bis(imido) N=U=N interaction. However, the calculations suggest that the multiple bonding in the oxo imido complexes is less covalent than that in the bis(imido) analogues.
- Published
- 2006
22. Synthesis and reactivity of the imido analogues of the uranyl ion
- Author
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James M. Boncella, Enrique R. Batista, P. Jeffrey Hay, Brian L. Scott, and Trevor W. Hayton
- Subjects
Stereochemistry ,Ligand ,Dimer ,General Chemistry ,Triple bond ,Uranyl ,Biochemistry ,Medicinal chemistry ,Chemical synthesis ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Pyridine ,Reactivity (chemistry) ,Lewis acids and bases - Abstract
Addition of 1.5 equiv of I2 to a THF solution of UI3(THF)4, containing either 6 equiv of tBuNH2 or 2 equiv of RNH2 (R = Ph, 3,5-(CF3)2C6H3, 2,6-(iPr)2C6H3) and 4 equiv of NEt3, generates orange solutions containing U(NtBu)2I2(THF)2 (1) or U(NAr)2I2(THF)3 (Ar = Ph, 2; 3,5-(CF3)2C6H3, 3; 2,6-(iPr)2C6H3, 4), respectively, all of which can be isolated in good yields. Alternatively, 1 can be prepared by reaction of uranium metal with 3 equiv of I2 and 6 equiv of tBuNH2, also in good yield. Complexes 1-4 have been characterized by X-ray crystallography, and each of these complexes exhibits linear N-U-N linkages and short U-N bonds. Using density functional theory simulations of complexes 1 and 2, two triple bonds between the metal center and the nitrogen ligands were identified. Complexes 1 and 2 readily react with neutral Lewis bases such as pyridine or Ph3PO to form U(NR)2I2(L)2 (R = tBu, L = py, 5; Ph3PO, 7; R = Ph, L = py, 6; Ph3PO, 8), and with PMe3 to form U(NR)2I2(THF)(PMe3)2 (R = tBu, 9; Ph, 10). The solid-state molecular structures of 5, 7, and 9 have been determined by X-ray crystallography, and these complexes, like their parent compounds, exhibit linear N-U-N angles and short U-N bonds. Complexes 1 and 2 also react with AgOTf in CH2Cl2, forming U(NR)2(OTf)2(THF)3 (R = tBu, 11; Ph, 12) after recrystallization from THF. Crystals of 12 grown from CH2Cl2 were found to contain a dimer, [U(NPh)2(OTf)2(THF)2]2, a complex possessing bridging triflate groups.
- Published
- 2006
23. Electron Localization in the Ground State of the Ruthenium Blue Dimer
- Author
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Richard L. Martin and Enrique R. Batista
- Subjects
Dimer ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,Biochemistry ,Catalysis ,Electron localization function ,Ruthenium ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Condensed Matter::Strongly Correlated Electrons ,Density functional theory ,Singlet state ,Symmetry breaking ,Atomic physics ,Ground state - Abstract
The electronic structure of the ruthenium blue dimer was studied with hybrid density functional theory (DFT) and complete action space self-consistent field (CASSCF) calculations. Hybrid DFT was found to overestimate the stability of the lowest triplet which leads to predicting this state as the ground state. However, CASSCF gives a singlet ground state in agreement with experiment. The density of the CASSCF ground state is in good agreement with the broken symmetry state obtained from DFT. These two results lead to the interpretation that the ground state of the ruthenium blue dimer is a partially localized antiferromagnetically coupled singlet state that lies three-quarters of the way toward the weak coupling limit. The electrons were found to localize in the dπ manifold.
- Published
- 2007
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