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149 results on '"Todorova, Tanya K."'

1. Connecting Defects and Amorphization in UiO-66 and MIL-140 Metal-organic Frameworks: A Combined Experimental and Computational Study

Author

Bennett, Thomas D., Todorova, Tanya K., Baxter, Emma F., Reid, David. G., Gervais, Christel, Bueken, Bart, Van de Voorde, B., De Vos, Dirk, Keen, David A., and Mellot-Draznieks, Caroline

Subjects
Condensed Matter - Materials Science
Abstract

The mechanism and products of the structural collapse of the metal-organic frameworks (MOFs) UiO-66, MIL-140B and MIL-140C upon ball-milling are investigated through solid state 13C NMR and pair distribution function (PDF) studies, finding amorphization to proceed by the breaking of a fraction of metal-ligand bonding in each case. The amorphous products contain inorganic-organic bonding motifs reminiscent of the crystalline phases. Whilst the inorganic Zr6O4(OH)4 clusters of UiO-66 remain intact upon structural collapse, the ZrO backbone of the MIL-140 frameworks undergoes substantial distortion. Density functional theory calculations have been performed to investigate defective models of MIL-140B and show, through comparison of calculated and experimental 13C NMR spectra, that amorphization and defects in the materials are linked., Comment: 24 pages, 7 figures, 2 tables

Published
2015
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3. Biphasic water splitting by osmocene

Author

Ge, Peiyu, Todorova, Tanya K., Patir, Imren Hatay, Olaya, Astrid J., Vrubel, Heron, Mendez, Manuel, Hu, Xile, Corminboeuf, Clémence, and Girault, Hubert H.

Published
2012

4. A bioinspired molybdenum–copper molecular catalyst for CO2 electroreduction† †Electronic supplementary information (ESI) available: UV-Vis, NMR and IR spectra of 1; electrochemical characterizations of 1, along with catalytic studies; SEM images and EDS spectra of GC electrodes before and after CPE of 1; electrochemical characterizations of [Mo(O)(bdt)2][Et4N]2, along with catalytic studies; structural parameters, IR frequencies, and frontier molecular orbitals of 1 and intermediates; xyz coordinates of all intermediates. See DOI: 10.1039/d0sc01045f

Author

Mouchfiq, Ahmed, Todorova, Tanya K., Dey, Subal, Fontecave, Marc, and Mougel, Victor

Subjects
Chemistry, mental disorders
Abstract

A bimetallic Mo–Cu complex inspired by the active site of the carbon monoxide dehydrogenase enzyme mediates the electroreduction of carbon dioxide to formic acid., Non-noble metal molecular catalysts mediating the electrocatalytic reduction of carbon dioxide are still scarce. This work reports the electrochemical reduction of CO2 to formate catalyzed by the bimetallic complex [(bdt)MoVI(O)S2CuICN]2– (bdt = benzenedithiolate), a mimic of the active site of the Mo–Cu carbon monoxide dehydrogenase enzyme (CODH2). Infrared spectroelectrochemical (IR-SEC) studies coupled with density functional theory (DFT) computations revealed that the complex is only a pre-catalyst, the active catalyst being generated upon reduction in the presence of CO2. We found that the two-electron reduction of [(bdt)MoVI(O)S2CuICN]2– triggers the transfer of the oxo moiety to CO2 forming CO32– and the complex [(bdt)MoIVS2CuICN]2– and that a further one-electron reduction is needed to generate the active catalyst. Its protonation yields a reactive MoVH hydride intermediate which reacts with CO2 to produce formate. These findings are particularly relevant to the design of catalysts from metal oxo precursors.

Published
2020

5. Vanadium oxides on aluminum oxide supports. 1. Surface termination and reducibility of vanadium films on alpha-Al2O3(0001)

Author

Todorova, Tanya K., Ganduglia-Pirovano M.Veronica, and Sauer, Joachim

Subjects
Oxides -- Chemical properties, Aluminum oxide -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

A detailed study on the structure and vibrational properties of V2O3 monolayer films supported on alpha-Al2O3 is presented. The reducibility of supported films with different thickness and termination is characterized by the energy of oxygen defect formation.

Published
2005

14. Electroreduction of CO2 to Formate with Low Overpotential using Cobalt Pyridine Thiolate Complexes.

Author

Dey, Subal, Todorova, Tanya K., Fontecave, Marc, and Mougel, Victor

Subjects
*OVERPOTENTIAL, *COBALT, *ELECTROLYTIC reduction, *PYRIDINE, *DENSITY functional theory, *ELECTROCATALYSTS, *ELECTROCATALYSIS
Abstract

Electrocatalytic CO2 reduction to value‐added products provides a viable alternative to the use of carbon sources derived from fossil fuels. Carrying out these transformations at reasonable energetic costs, for example, with low overpotential, remains a challenge. Molecular catalysts allow fine control of activity and selectivity via tuning of their coordination sphere and ligand set. Herein we investigate a series of cobalt(III) pyridine‐thiolate complexes as electrocatalysts for CO2 reduction. The effect of the ligands and proton sources on activity was examined. We identified bipyridine bis(2‐pyridinethiolato) cobalt(III) hexaflurophosphate as a highly selective catalyst for formate production operating at a low overpotential of 110 mV with a turnover frequency (TOF) of 10 s−1. Electrokinetic analysis coupled with density functional theory (DFT) computations established the mechanistic pathway, highlighting the role of metal hydride intermediates. The catalysts deactivate via the formation of stable cobalt carbonyl complexes, but the active species could be regenerated upon oxidation and release of coordinated CO ligands. [ABSTRACT FROM AUTHOR]

Published
2020
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18. Nonuniform temperature dependence of the reactivity of disordered VOx/κ-Al2O3(001) surfaces: A density functional theory based Monte Carlo study.

Author

Fortrie, Rémy, Todorova, Tanya K., Ganduglia-Pirovano, M. Verónica, and Sauer, Joachim

Subjects
*DENSITY, *THEORY, *MESOSCOPIC phenomena (Physics), *TEMPERATURE, *OXIDATION
Abstract

Periodic density functional theory (DFT) calculations concerning VOx/κ-Al2O3(001) surfaces are used for parametrizing Monte Carlo simulations performed on a mesoscopic scale surface sample (41.95×48.80 nm2). New structural and chemical information are then obtained that are not accessible from DFT calculations: segregation, short- and long-range ordering, and the effect of the temperature on the reducibility. The reducibility of the surface is investigated for locating chemical potential regions where the catalyst is especially reactive for oxidation reactions. Comparison with the V2O5(001) surface at catalytic conditions (800 K, 1 bar) is performed. The reducibility exhibits an unexpectedly strong temperature dependence. [ABSTRACT FROM AUTHOR]

Published
2008
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19. Oxygen adsorption on Mo(112) surface studied by ab initio genetic algorithm and experiment.

Author

Sierka, Marek, Todorova, Tanya K., Sauer, Joachim, Kaya, Sarp, Stacchiola, Dario, Weissenrieder, Jonas, Shaikhutdinov, Shamil, and Freund, Hans-Joachim

Subjects
*OXYGEN, *GENETIC algorithms, *EXPERIMENTS, *DENSITY, *ATOMIC models, *PHOTOELECTRON spectroscopy, *SCANNING tunneling microscopy
Abstract

Density functional theory in combination with genetic algorithm is applied to determine the atomic models of p(1×2) and p(1×3) surface structures observed upon oxygen adsorption on a Mo(112) surface. The authors’ simulations reveal an unusual flexibility of Mo(112) resulting in oxygen-induced reconstructions and lead to more stable structures than any suggested so far. Comparison of the stabilities of the predicted models shows that different p(1×2) and p(1×3) structures may coexist over a wide range of oxygen pressures. A pure p(1×2) structure can be obtained only in a narrow region of oxygen pressures. In contrast, a pure p(1×3) structure cannot exist as a stable phase. The results of simulations are fully supported by a multitude of experimental data obtained from low energy electron diffraction, x-ray photoelectron spectroscopy, and scanning tunneling microscopy. [ABSTRACT FROM AUTHOR]

Published
2007
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20. DFT and CASPT2 analysis of polymetallic uranium nitride and oxide complexes: how theory can help when X-ray analysis is inadequate

Author

Todorova, Tanya K., Gagliardi, Laura, Walensky, Justin R., Miller, Kevin A., and Evans, William J.

Subjects
Crystallography -- Usage, Density functionals -- Usage, Nitrides -- Chemical properties, Organometallic compounds -- Structure, Organometallic compounds -- Chemical properties, Quantum theory -- Usage, Uranium -- Chemical properties, Chemistry
Abstract

Density functional theory and multiconfigurational quantum chemical studies were performed to differentiate nitride versus oxide in polymetallic uranium molecules containing [(N).sup.3-] and [(O).sup.2-]. The crystallographic data obtained provide insight into the electronic structure and unique chemical bonding of uranium polymetallic compounds.

Published
2010

21. Structural, spectroscopic, and multiconfigurational quantum chemical investigations of the electron-rich metal-metal triple-bonded [Tc.sub.2][X.sub.4][(P[Me.sub.3]).sub.4] (X = Cl, Br) complexes

Author

Poineau, Frederic, Forster, Paul M., Todorova, Tanya K., Gagliardi, Laura, Sattelberger, Alfred P., and Czerwinski, Kenneth R.

Subjects
Density functionals -- Usage, Methyl groups -- Structure, Methyl groups -- Chemical properties, Quantum chemistry -- Analysis, X-rays -- Diffraction, X-rays -- Usage, Chemistry
Published
2010

22. The Ru-Hbpp water oxidation catalyst

Author

Bozoglian, Fernando, Romain, Sophie, Ertem, Mehmed Z., Todorova, Tanya K., Sens, Cristina, Mola, Joaquim, Rodriguez, Montserrat, Romero, Isabel, Benet-Buchholz, Jordi, Fontrodona, Xavier, Cramer, Christopher J., Gagliardi, Laura, and Llobet, Antoni

Subjects
Ultraviolet spectroscopy -- Usage, Density functionals -- Usage, Catalysis -- Analysis, Oxidation-reduction reaction -- Analysis, Ruthenium -- Chemical properties, Spectrum analysis -- Usage, Chemistry
Abstract

The characterization of the Ru-Hbpp water oxidation catalyst is carried out by using structural, spectroscopic, kinetic and electrochemical analyses. The Ru-Hbpp complex is studied under catalytic conditions as a function of time by using manometric measurements and mass spectrometry.

Published
2009

23. Theoretical study of the gas-phase chemiionization reactions La+O and La+[O.sub.2]

Author

Todorova, Tanya K., Infante, Ivan, Gagliardi, Laura, and Dyke, John M.

Subjects
Lanthanum -- Chemical properties, Lanthanum -- Structure, Quantum chemistry -- Research, Chemicals, plastics and rubber industries
Abstract

The La+O and La+[O.sub.2] chemiionization reactions are investigated using quantum chemical methods. During the study potential energy curves are computed for a number of states of LaO, La[O.sup.*] and La[O.sup.+].

Published
2008

27. Structural, Spectroscopic, and Multiconfigurational Quantum Chemical Investigations of the Electron-Rich Metal−Metal Triple-Bonded Tc2X4(PMe3)4(X = Cl, Br) Complexes

Author

Poineau, Frederic, Forster, Paul M., Todorova, Tanya K., Gagliardi, Laura, Sattelberger, Alfred P., and Czerwinski, Kenneth R.

Abstract

The compounds Tc2Cl4(PMe3)4and Tc2Br4(PMe3)4were formed from the reaction between (n-Bu4N)2Tc2X8(X = Cl, Br) and trimethylphosphine. The Tc(II) dinuclear species were characterized by single-crystal XRD, UV−visible spectroscopy, and cyclic voltammetry techniques, and the results are compared to those obtained from density functional theory and multiconfigurational (CASSCF/CASPT2) quantum chemical studies. The compound Tc2Cl4(PMe3)4crystallizes in the monoclinic space group C2/c[a= 17.9995(9) Å, b= 9.1821(5) Å, c= 17.0090(9) Å, β = 115.4530(10)°] and is isostructural to M2Cl4(PMe3)4(M = Re, Mo, W) and to Tc2Br4(PMe3)4. The metal−metal distance (2.1318(2) Å) is similar to the one found in Tc2Br4(PMe3)4(2.1316(5) Å). The calculated molecular structures of the ground states are in excellent agreement with the structures determined experimentally. Calculations of effective bond orders for Tc2X82−and Tc2X4(PMe3)4(X = Cl, Br) indicate stronger π bonds in the Tc24+core than in Tc26+core. The electronic spectra were recorded in benzene and show a series of low intensity bands in the range 10 000−26 000 cm−1. Assignment of the bands as well as computing their excitation energies and intensities were performed at both TD-DFT and CASSCF/CASPT2 levels of theory. Calculations predict that the lowest energy band corresponds to the δ* → σ* transition, the difference between calculated and experimental values being 228 cm−1for X = Cl and 866 cm−1for X = Br. The next bands are attributed to δ* → π*, δ → σ*, and δ → π* transitions. The cyclic voltammograms exhibit two reversible waves and indicate that Tc2Br4(PMe3)4exhibits more positive oxidation potentials than Tc2Cl4(PMe3)4.This phenomenon is discussed and ascribed to stronger metal (d) to halide (d) back bonding in the bromo complex. Further analysis indicates that Tc(II) dinuclear species containing π-acidic phosphines are more difficult to oxidize, and a correlation between oxidation potential and phosphine acidity was established.

Published
2024
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28. Molecular and Electronic Structure of Re2Br4(PMe3)(4)

Author

Johnstone, Erik V., Poineau, Frederic, Todorova, Tanya K., Forster, Paul M., Sørensen, Lasse K., Fernández Galván, Ignacio, Lindh, Roland, Czerwinski, Kenneth R., Sattelberger, Alfred P., Johnstone, Erik V., Poineau, Frederic, Todorova, Tanya K., Forster, Paul M., Sørensen, Lasse K., Fernández Galván, Ignacio, Lindh, Roland, Czerwinski, Kenneth R., and Sattelberger, Alfred P.

Abstract

The dinuclear rhenium(II) complex Re2Br4(PMe3)(4) was prepared from the reduction of [Re2Br8](2-) with (n-Bu4N)BH4 in the presence of PMe3 in propanol. The complex was characterized by single-crystal X-ray diffraction (SCXRD) and UV-visible spectroscopy. It crystallizes in the monoclinic C2/c space group and is isostructural with its molybdenum and technetium analogues. The Re-Re distance (2.2521(3) angstrom) is slightly longer than the one in Re2Cl4(PMe3)(4) (2.247(1) angstrom). The molecular and electronic structure of Re2X4(PMe3)(4) (X = Cl, Br) were studied by multiconfigurational quantum chemical methods. The computed ground-state geometry is in excellent agreement with the experimental structure determined by SCXRD. The calculated total bond order (2.75) is consistent with the presence of an electron-rich triple bond and is similar to the one found for Re2Cl4(PMe3)(4). The electronic absorption spectrum of Re2Br4(PMe3)(4) was recorded in benzene and shows a series of low-intensity bands in the range 10 000-26 000 cm(-1). The absorption bands were assigned based on calculations of the excitation energies with the multireference wave functions followed by second-order perturbation theory using the CASSCF/CASPT2 method. Calculations predict that the lowest energy band corresponds to the delta* -> sigma* transition, while the next higher energy bands were attributed to the delta* -> pi*, delta -> sigma*, and delta -> pi* transitions.

Published
2016
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29. Molecular Level Characterization of the Structure and Interactions in Peptide-Functionalized Metal-Organic Frameworks

Author

Todorova, Tanya K., primary, Rozanska, Xavier, additional, Gervais, Christel, additional, Legrand, Alexandre, additional, Ho, Linh N., additional, Berruyer, Pierrick, additional, Lesage, Anne, additional, Emsley, Lyndon, additional, Farrusseng, David, additional, Canivet, Jérôme, additional, and Mellot-Draznieks, Caroline, additional

Published
2016
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30. Molecular and Electronic Structure of Re2Br4(PMe3)4

Author

Johnstone, Erik V., primary, Poineau, Frederic, additional, Todorova, Tanya K., additional, Forster, Paul M., additional, Sørensen, Lasse K., additional, Fdez. Galván, Ignacio, additional, Lindh, Roland, additional, Czerwinski, Kenneth R., additional, and Sattelberger, Alfred P., additional

Published
2016
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34. Controlling Hydrogen Evolution during Photoreduction of CO2to Formic Acid Using [Rh(R-bpy)(Cp*)Cl]+Catalysts: A Structure–Activity Study

Author

Todorova, Tanya K., Huan, Tran Ngoc, Wang, Xia, Agarwala, Hemlata, and Fontecave, Marc

Abstract

The photochemical reduction of CO2to formic acid catalyzed by a series of [Rh(4,4′-R-bpy)(Cp*)Cl]+and [Rh(5,5′-COOH-bpy)(Cp*)Cl]+complexes (Cp* = pentamethylcyclopentadienyl, bpy = 2,2′-bipyridine, and R = OCH3, CH3, H, COOC2H5, CF3, NH2, or COOH) was studied to assess how modifications in the electronic structure of the catalyst affect its selectivity, defined as the HCOOH:H2product ratio. A direct molecular-level influence of the functional group on the initial reaction rate for CO2versus proton reduction reactions was established. Density functional theory computations elucidated for the first time the respective role of the [RhH] and [Cp*H] tautomers, recognizing rhodium hydride as the key player for both reactions. In particular, our calculations explain the observed tendency of electron-donating substituents to favor CO2reduction by means of decreasing the hydricity of the Rh–H bond, resulting in a lower hydride transfer barrier toward formic acid production as compared to substituents with an electron-withdrawing nature that favor more strongly the reduction of protons to hydrogen.

Published
2019
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38. The cis-[Ru-II(bpy)(2)(H2O)(2)](2+) Water-Oxidation Catalyst Revisited

Author

Sala, Xavier, Ertem, Mehmed Z., Vigara, Laura, Todorova, Tanya K., Chen, Weizhong, Rocha, Reginaldo C., Aquilante, Francesco, Cramer, Christopher J., Gagliardi, Laura, Llobet, Antoni, Sala, Xavier, Ertem, Mehmed Z., Vigara, Laura, Todorova, Tanya K., Chen, Weizhong, Rocha, Reginaldo C., Aquilante, Francesco, Cramer, Christopher J., Gagliardi, Laura, and Llobet, Antoni

Published
2010
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39. Understanding, Controlling and Programming Cooperativity in Self-Assembled Polynuclear Complexes in Solution

Author

Riis-Johannessen, Thomas, Favera, Natalia Dalla, Todorova, Tanya K., Huber, Stefan M., Gagliardi, Laura, Piguet, Claude, Riis-Johannessen, Thomas, Favera, Natalia Dalla, Todorova, Tanya K., Huber, Stefan M., Gagliardi, Laura, and Piguet, Claude

Abstract

Deviations from statistical binding, that is cooperativity, in self-assembled polynuclear complexes partly result from intermetallic interactions Delta E-M,E-M, whose magnitudes in solution depend on a balance between electrostatic repulsion and solvation energies. These two factors have been reconciled in a simple point-charge model, which suggests severe and counter-intuitive deviations from predictions based solely on the Coulomb law when considering the variation of Delta E-M,E-M with metallic charge and intermetallic separation in linear polynuclear helicates. To demonstrate this intriguing behaviour, the ten microscopic interactions that define the thermodynamic formation constants of some twenty-nine homometallic and lieterometallic polynuclear triple-stranded helicates obtained from the coordination of the segmental ligands L1-L11 with Zn2+ (a spherical d-block cation) and Lu3+ (a spherical 4f-block cation), have been extracted by using the site binding model. As predicted, but in contrast with the simplistic coulombic approach, the apparent intramolecular intermetallic interactions in solution are found to be i) more repulsive at long distance (Delta E-1-4(Lu,Lu) > Delta E-1-2(Lu,Lu)), ii) of larger magnitude when Zn2+ replaces Lu3+ (Delta E-1-2(Zn,Lu) > Delta E-1-2(Lu,Lu)) and iii) attractive between two triply charged cations held at some specific distance (Delta E-1-3(Lu,Lu) < 0). The consequences of these trends are discussed for the design of polynuclear complexes in solution.

Published
2010
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46. The cis‐[RuII(bpy)2(H2O)2]2+ Water‐Oxidation Catalyst Revisited

Author

Sala, Xavier, primary, Ertem, Mehmed Z., additional, Vigara, Laura, additional, Todorova, Tanya K., additional, Chen, Weizhong, additional, Rocha, Reginaldo C., additional, Aquilante, Francesco, additional, Cramer, Christopher J., additional, Gagliardi, Laura, additional, and Llobet, Antoni, additional

Published
2010
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50. The Ru−Hbpp Water Oxidation Catalyst

Author

Bozoglian, Fernando, primary, Romain, Sophie, additional, Ertem, Mehmed Z., additional, Todorova, Tanya K., additional, Sens, Cristina, additional, Mola, Joaquim, additional, Rodríguez, Montserrat, additional, Romero, Isabel, additional, Benet-Buchholz, Jordi, additional, Fontrodona, Xavier, additional, Cramer, Christopher J., additional, Gagliardi, Laura, additional, and Llobet, Antoni, additional

Published
2009
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