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Tricoire M, Mahieu N, Simler T, Nocton G. Intermediate Valence States in Lanthanide Compounds. Chemistry 2021; 27:6860-6879. [PMID: 33340383 PMCID: PMC7610675 DOI: 10.1002/chem.202004735] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Indexed: 12/31/2022]
Abstract
Over more than 50 years, intermediate valence states in lanthanide compounds have often resulted in unexpected or puzzling spectroscopic and magnetic properties. Such experimental singularities could not be rationalised until new theoretical models involving multiconfigurational electronic ground states were established. In this minireview, the different singularities that have been observed among lanthanide complexes are highlighted, the models used to rationalise them are detailed and how such electronic effects may be adjusted depending on energy and symmetry considerations is considered. Understanding and tuning the ground-state multiconfigurational behaviour in lanthanide complexes may open new doors to modular and unusual reactivities.
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Affiliation(s)
- Maxime Tricoire
- LCM, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Route de Saclay, 91128, Palaiseau, cedex, France
| | - Nolwenn Mahieu
- LCM, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Route de Saclay, 91128, Palaiseau, cedex, France
| | - Thomas Simler
- LCM, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Route de Saclay, 91128, Palaiseau, cedex, France
| | - Grégory Nocton
- LCM, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Route de Saclay, 91128, Palaiseau, cedex, France
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2
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Lukens WW, Booth CH, Walter MD. Experimental evaluation of the stabilization of the COT orbitals by 4f orbitals in COT 2Ce using a Hubbard model. Dalton Trans 2021; 50:2530-2535. [PMID: 33522542 DOI: 10.1039/d0dt03897k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Significant orbital mixing is rare in lanthanide complexes because of the limited radial extent of the 4f orbitals, which results in a generally small stabilization due to 4f orbital interactions. Nevertheless, even a small amount of additional stabilization could enhance lanthanide separations. One lanthanide complex in which orbital mixing has been extensively studied both experimentally and computationally is cerocene, COT2Ce, where COT is cyclooctatetraene. This compound has a singlet ground state with a low-lying, triplet excited state. Previous fluorescence studies on trimethylsilyl-substituted cerocenes indicate the triplet state is 0.4 eV higher in energy than the singlet state. In addition, computational studies predict that the triplet is 0.3 to 1 eV higher in energy than the singlet. The synthesis of highly pure COT2Ce by Walter and Andersen allowed its physical properties to be accurately measured. Using these measurements, we evaluate the stabilization of the 4f orbitals using two, independent approaches. A Hubbard model is used to evaluate the stabilization of the ground state due to orbital mixing. This stabilization, which is also the singlet-triplet gap, is -0.29 eV using this model. This gap was also from the temperature independent paramagnetism of COT2Ce, which yielded a value of -0.32 eV.
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Affiliation(s)
- Wayne W Lukens
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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Smiles DE, Batista ER, Booth CH, Clark DL, Keith JM, Kozimor SA, Martin RL, Minasian SG, Shuh DK, Stieber SCE, Tyliszczak T. The duality of electron localization and covalency in lanthanide and actinide metallocenes. Chem Sci 2020; 11:2796-2809. [PMID: 34084340 PMCID: PMC8157540 DOI: 10.1039/c9sc06114b] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 02/04/2020] [Indexed: 12/14/2022] Open
Abstract
Previous magnetic, spectroscopic, and theoretical studies of cerocene, Ce(C8H8)2, have provided evidence for non-negligible 4f-electron density on Ce and implied that charge transfer from the ligands occurs as a result of covalent bonding. Strong correlations of the localized 4f-electrons to the delocalized ligand π-system result in emergence of Kondo-like behavior and other quantum chemical phenomena that are rarely observed in molecular systems. In this study, Ce(C8H8)2 is analyzed experimentally using carbon K-edge and cerium M5,4-edge X-ray absorption spectroscopies (XAS), and computationally using configuration interaction (CI) calculations and density functional theory (DFT) as well as time-dependent DFT (TDDFT). Both spectroscopic approaches provide strong evidence for ligand → metal electron transfer as a result of Ce 4f and 5d mixing with the occupied C 2p orbitals of the C8H8 2- ligands. Specifically, the Ce M5,4-edge XAS and CI calculations show that the contribution of the 4f1, or Ce3+, configuration to the ground state of Ce(C8H8)2 is similar to strongly correlated materials such as CeRh3 and significantly larger than observed for other formally Ce4+ compounds including CeO2 and CeCl6 2-. Pre-edge features in the experimental and TDDFT-simulated C K-edge XAS provide unequivocal evidence for C 2p and Ce 4f covalent orbital mixing in the δ-antibonding orbitals of e2u symmetry, which are the unoccupied counterparts to the occupied, ligand-based δ-bonding e2u orbitals. The C K-edge peak intensities, which can be compared directly to the C 2p and Ce 4f orbital mixing coefficients determined by DFT, show that covalency in Ce(C8H8)2 is comparable in magnitude to values reported previously for U(C8H8)2. An intuitive model is presented to show how similar covalent contributions to the ground state can have different impacts on the overall stability of f-element metallocenes.
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Affiliation(s)
- Danil E Smiles
- Lawrence Berkeley National Laboratory Berkeley California 94720 USA
| | | | - Corwin H Booth
- Lawrence Berkeley National Laboratory Berkeley California 94720 USA
| | - David L Clark
- Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | | | - Stosh A Kozimor
- Los Alamos National Laboratory Los Alamos New Mexico 87545 USA
| | | | | | - David K Shuh
- Lawrence Berkeley National Laboratory Berkeley California 94720 USA
| | | | - Tolek Tyliszczak
- Lawrence Berkeley National Laboratory Berkeley California 94720 USA
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Halbach RL, Nocton G, Booth CH, Maron L, Andersen RA. Cerium Tetrakis(tropolonate) and Cerium Tetrakis(acetylacetonate) Are Not Diamagnetic but Temperature-Independent Paramagnets. Inorg Chem 2018; 57:7290-7298. [PMID: 29863340 DOI: 10.1021/acs.inorgchem.8b00928] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new synthesis of cerium tetrakis(tropolonate), Ce(trop)4, where trop is deprotonated 2-hydroxy-2,4,6-cycloheptatrienone) or Ce(O2C7H5)4, is developed that results in dark-purple crystals whose X-ray crystal structure shows that the geometry of the eight-coordinate compound closely resembles a D2 d dodecahedron, based on shape parameters. The magnetic susceptibility as a function of the temperature (4-300 K) shows that it is a temperature-independent paramagnet, χ = 1.2(3) × 10-4 emu/mol, and the LIII-edge X-ray absorption near-edge structure spectrum shows that the molecule is multiconfigurational, comprised of a f1:f0 configuration mixture in a 50:50 ratio. Ce(acac)4 and Ce(tmtaa)2 (where acac is acetylacetonate and tmtaaH2 is tetramethyldibenzotetraaza[14]annulene) have similar physical properties, as does the solid-state compound CeO2. The concept is advanced that trop-, acac-, tmtaa2-, cot2-, and O2- are redox-active ligands that function as electron donors, rendering the classification of these compounds according to their oxidation numbers misleading because their magnetic susceptibilities, χ, are positive and their effective magnetic moments, μeff, lie in the range of 0.1-0.7 μB at 300 K.
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Affiliation(s)
- Robert L Halbach
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - Grégory Nocton
- Department of Chemistry , University of California , Berkeley , California 94720 , United States.,Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,LCM, CNRS , Ecole Polytechnique, Université Paris Saclay , 91128 Palaiseau , France
| | - Corwin H Booth
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Laurent Maron
- LPCNO, UMR 5215, CNRS, INSA, UPS , Université de Toulouse , 31000 Toulouse , France
| | - Richard A Andersen
- Department of Chemistry , University of California , Berkeley , California 94720 , United States.,Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
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Coreno M, de Simone M, Green JC, Kaltsoyannis N, Coates R, Hunston C, Narband N, Sella A. Variable photon energy photoelectron spectroscopy of tris-cyclopentadienyl lanthanides. Dalton Trans 2014; 43:5134-41. [DOI: 10.1039/c3dt53512f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gas-phase photoelectron spectra are presented for LnCp3 (Cp = η-C5H5; Ln = Pr, Nd, Sm) in which f ionization gives rise to bands associated with 4fn configurations in addition to the expected 4fn−1 bands.
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Affiliation(s)
| | | | | | | | - Rosemary Coates
- Department of Chemistry
- University College London
- London WC1H 0AJ, UK
| | - Charlene Hunston
- Department of Chemistry
- University College London
- London WC1H 0AJ, UK
| | - Naima Narband
- Department of Chemistry
- University College London
- London WC1H 0AJ, UK
| | - Andrea Sella
- Department of Chemistry
- University College London
- London WC1H 0AJ, UK
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Denning RG, Harmer J, Green JC, Irwin M. Covalency in the 4f Shell of tris-Cyclopentadienyl Ytterbium (YbCp3)—A Spectroscopic Evaluation. J Am Chem Soc 2011; 133:20644-60. [DOI: 10.1021/ja209311g] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Robert G. Denning
- Department of Chemistry and ‡Center for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Jeffrey Harmer
- Department of Chemistry and ‡Center for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Jennifer C. Green
- Department of Chemistry and ‡Center for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Mark Irwin
- Department of Chemistry and ‡Center for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
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Zhao YX, Wu XN, Ma JB, He SG, Ding XL. Characterization and reactivity of oxygen-centred radicals over transition metal oxide clusters. Phys Chem Chem Phys 2011; 13:1925-38. [DOI: 10.1039/c0cp01171a] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Booth CH, Kazhdan D, Werkema EL, Walter MD, Lukens WW, Bauer ED, Hu YJ, Maron L, Eisenstein O, Head-Gordon M, Andersen RA. Intermediate-valence tautomerism in decamethylytterbocene complexes of methyl-substituted bipyridines. J Am Chem Soc 2010; 132:17537-49. [PMID: 21090709 DOI: 10.1021/ja106902s] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Multiconfigurational, intermediate valent ground states are established in several methyl-substituted bipyridine complexes of bis(pentamethylcyclopentadienyl)ytterbium, Cp2*Yb (Me(x)-bipy). In contrast to Cp2*Yb(bipy) and other substituted-bipy complexes, the nature of both the ground state and the first excited state are altered by changing the position of the methyl or dimethyl substitutions on the bipyridine rings. In particular, certain substitutions result in multiconfigurational, intermediate valent open-shell singlet states in both the ground state and the first excited state. These conclusions are reached after consideration of single-crystal X-ray diffraction (XRD), the temperature dependence of X-ray absorption near-edge structure (XANES), extended X-ray absorption fine-structure (EXAFS), and magnetic susceptibility data, and are supported by CASSCF-MP2 calculations. These results place the various Cp2*Yb(bipy) complexes in a new tautomeric class, that is, intermediate-valence tautomers.
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Affiliation(s)
- Corwin H Booth
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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Coreno M, de Simone M, Coates R, Denning MS, Denning RG, Green JC, Hunston C, Kaltsoyannis N, Sella A. Variable Photon Energy Photoelectron Spectroscopy and Magnetism of YbCp3 and LuCp3. Organometallics 2010. [DOI: 10.1021/om100240m] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marcello Coreno
- CNR-IMIP, GasPhase Beamline@Elettra and Monterotondo, 00016 Roma, Italy
| | | | - Rosemary Coates
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, U.K
| | - Mark S. Denning
- Department of Chemistry, Oxford University, South Parks Road, Oxford OX1 3QR, U.K
| | - Robert G. Denning
- Department of Chemistry, Oxford University, South Parks Road, Oxford OX1 3QR, U.K
| | - Jennifer C. Green
- Department of Chemistry, Oxford University, South Parks Road, Oxford OX1 3QR, U.K
| | - Charlene Hunston
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, U.K
| | - Nikolas Kaltsoyannis
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, U.K
| | - Andrea Sella
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, U.K
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Wu XN, Zhao YX, Xue W, Wang ZC, He SG, Ding XL. Active sites of stoichiometric cerium oxide cations (CemO2m+) probed by reactions with carbon monoxide and small hydrocarbon molecules. Phys Chem Chem Phys 2010; 12:3984-97. [DOI: 10.1039/b925294k] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Booth CH, Walter MD, Kazhdan D, Hu YJ, Lukens WW, Bauer ED, Maron L, Eisenstein O, Andersen RA. Decamethylytterbocene complexes of bipyridines and diazabutadienes: multiconfigurational ground states and open-shell singlet formation. J Am Chem Soc 2009; 131:6480-91. [PMID: 19385617 DOI: 10.1021/ja809624w] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Partial ytterbium f-orbital occupancy (i.e., intermediate valence) and open-shell singlet formation are established for a variety of bipyridine and diazabutadiene adducts with decamethylytterbocene, (C(5)Me(5))(2)Yb, abbreviated as Cp*(2)Yb. Data used to support this claim include ytterbium valence measurements using Yb L(III)-edge X-ray absorption near-edge structure spectroscopy, magnetic susceptibility, and complete active space self-consistent field (CASSCF) multiconfigurational calculations, as well as structural measurements compared to density functional theory calculations. The CASSCF calculations indicate that the intermediate valence is the result of a multiconfigurational ground-state wave function that has both an open-shell singlet f(13)(pi*)(1), where pi* is the lowest unoccupied molecular orbital of the bipyridine or diazabutadiene ligands, and a closed-shell singlet f(14) component. A number of other competing theories for the unusual magnetism in these materials are ruled out by the lack of temperature dependence of the measured intermediate valence. These results have implications for understanding chemical bonding not only in organolanthanide complexes but also for f-element chemistry in general, as well as understanding magnetic interactions in nanoparticles and devices.
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Affiliation(s)
- Corwin H Booth
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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Maron L, Eisenstein O, Andersen RA. The Bond between CO and Cp′3U in Cp′3U(CO) Involves Back-bonding from the Cp′3U Ligand-Based Orbitals of π-Symmetry, where Cp′ Represents a Substituted Cyclopentadienyl Ligand. Organometallics 2009. [DOI: 10.1021/om801098b] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Laurent Maron
- LPCNO, Université de Toulouse, INSA, UPS, LPCNO, 135 Avenue de Rangueil, F-31077 Toulouse, France, and CNRS, LPCNO, F-31077 Toulouse, France
| | - Odile Eisenstein
- Institut Charles Gerhardt, Université Montpellier 2, CNRS 5253, case courrier 1501, Place E. Bataillon, 34095 Montpellier France
| | - Richard A. Andersen
- Department of Chemistry and Chemical Sciences Division of Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720-1460
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Walter MD, Booth CH, Lukens WW, Andersen RA. Cerocene Revisited: The Electronic Structure of and Interconversion Between Ce2(C8H8)3 and Ce(C8H8)2. Organometallics 2009. [DOI: 10.1021/om7012327] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Marc D. Walter
- Department of Chemistry and Chemical Sciences Division of Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720
| | - Corwin H. Booth
- Department of Chemistry and Chemical Sciences Division of Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720
| | - Wayne W. Lukens
- Department of Chemistry and Chemical Sciences Division of Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720
| | - Richard A. Andersen
- Department of Chemistry and Chemical Sciences Division of Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720
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Coates R, Coreno M, DeSimone M, Green JC, Kaltsoyannis N, Kerridge A, Narband N, Sella A. A mystery solved? Photoelectron spectroscopic and quantum chemical studies of the ion states of CeCp3+. Dalton Trans 2009:5943-53. [DOI: 10.1039/b902263e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ashley A, Balazs G, Cowley A, Green J, Booth CH, O'Hare D. Bis(permethylpentalene)cerium ? another ambiguity in lanthanide oxidation state. Chem Commun (Camb) 2007:1515-7. [PMID: 17406692 DOI: 10.1039/b700303j] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ce(eta(8)-C(8)Me(6))(2) exists in a valency close to Ce(iii) with some Ce(iv) and provides an example of the Kondo effect in a discrete molecule.
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Affiliation(s)
- Andrew Ashley
- Chemistry Research Laboratory, Mansfield Rd, Oxford, UK
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Casely IJ, Liddle ST, Blake AJ, Wilson C, Arnold PL. Tetravalent cerium carbene complexes. Chem Commun (Camb) 2007:5037-9. [DOI: 10.1039/b713041d] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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