Metal and Ligand K-Edge XAS of Organotitanium Complexes:  Metal 4p and 3d Contributions to Pre-edge Intensity and Their Contributions to Bonding

DeBeer, Serena; Brant, Patrick; Solomon, Edward I.

doi:10.1021/ja044827v

Cited by 131 publications

(161 citation statements)

References 44 publications

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“…Hence, in the solution-phase DFT calculations the 4 t 2 * orbitals are reasonably described as resulting from primarily metal n d and S 3p mixing. Because the solution-phase molecular orbital picture agreed better with previous theoretical models used to evaluate MS 4 2- , MO 4 2- , and MCl 4 ligand K-edge XAS spectra, 58,59,73-77 and in light of the gas- vs. solution-phase TDDFT results ( vide infra ), the solution-phase DFT data appeared to provide a more relevant model than the gas-phase calculations. Consistently, others have observed that including solvent dielectrics improves DFT agreement with XAS experimental data for anionic species.…”

Section: Resultssupporting

confidence: 51%

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Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS₄²⁻(M = Cr, Mo, W) dianions

et al. 2014

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Herein, we have evaluated relative changes in M–S electronic structure and orbital mixing in Group 6 MS42- dianions using solid- and solution-phase S K-edge X-ray absorption spectroscopy (XAS; M = Mo, W), as well as density functional theory (DFT; M = Cr, Mo, W) and time-dependent density functional theory (TDDFT) calculations. To facilitate comparison with solution measurements (conducted in acetonitrile), theoretical models included gas-phase calculations as well as those that incorporated an acetonitrile dielectric, the latter of which provided better agreement with experiment. Two pre-edge features arising from S 1s → e* and t2* electron excitations were observed in the S K-edge XAS spectra and were reasonably assigned as 1A1 → 1T2 transitions. For MoS42-, both solution-phase pre-edge peak intensities were consistent with results from the solid-state spectra. For WS42-, solution- and solid-state pre-edge peak intensities for transitions involving e* were equivalent, while transitions involving the t2* orbitals were less intense in solution. Experimental and computational results have been presented in comparison to recent analyses of MO42- dianions, which allowed M–S and M–O orbital mixing to be evaluated as the principle quantum number (n) for the metal valence d orbitals increased (3d, 4d, 5d). Overall, the M–E (E = O, S) analyses revealed distinct trends in orbital mixing. For example, as the Group 6 triad was descended, e* (π*) orbital mixing remained constant in the M–S bonds, but increased appreciably for M–O interactions. For the t2* orbitals (σ* + π*), mixing decreased slightly for M–S bonding and increased only slightly for the M–O interactions. These results suggested that the metal and ligand valence orbital energies and radial extensions delicately influenced the orbital compositions for isoelectronic ME42- (E = O, S) dianions.

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Section: Resultssupporting

confidence: 51%

“…41,47,59,70,71,77,81-88 The computed spectra were carried out using linear response theory, based on density functional theory. This formalism is commonly referred in the community as TDDFT as it is from the time-dependent perturbation theory to DFT.…”

Section: Resultsmentioning

confidence: 99%

Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS₄²⁻(M = Cr, Mo, W) dianions

et al. 2014

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“…36 ,4o,s4 The TD DFT simulated CI K-edge XAS for (CsMe5)2MCI2 (Ti, 1; Zr, 2; andHf, 3) agree well with the experimental data and show two pre-edge features for 1 and 2, and tlu'ee features for 3, Figure 6. 3 is attributed to a CI Is -;.…”

Section: Hybrid-dft Spectral Simulations Time Dependent Density Funcsupporting

confidence: 61%

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

et al. 2009

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Abstract:We describe the use of CI K-edge X-ray Absorption Spectroscopy (XAS) and both ground state and time-dependent hybrid-Density Functional Theory (OFT) to probe electronic structure and determine the degree of orbital mixing in M-CI bonds for (C5Me5hMCI2 (M =Ti, 1; Zr, calculations as a guide to interpret the experimental CI K-edge XAS, these experiments suggest that when evaluating An-CI bonding, both 5f-and 6d-orbitals should be considered. For (C5Me5)zThCb, the calculations and XAS indicate that the 5f-and 6d-orbitals are nearly degenerate and heavily mixed. In contrast, the 5f-and 6d-orbitals in (C5Mes)2UCl z are no longer degenerate, and fall in two distinct energy groupings. The Sf-orbitals are lowest in energy and split into a 5-over-2 pattern with the high lying U 6d-orbitals split in a 4-over-1 pattern,the latter of which is similar to the d-orbital splitting in group IV transition metal (C 5 Rs)zMCl z (R =H, Me)compounds. Time dependent-OFT (TO-OFT) was used to calculate the energies and intensities of CI is transitions into empty metal based orbitals containing CI 3p character, and provide simulated CI K-edge XAS spectra for 1-4. However, for 5, which has two unpaired electrons, analogous information was obtained from transition dipole calculations. The simulations provide additional confidence in the interpretation of spectra based on ground state calculations.Overall, this study demonstrates that CI K-edge XAS and DFT calculations represent powerful J20ls that can be used to experimentally evaluate electronic structure and covalency in actinide metal-ligand bonding. In addition, fhese results provide a framework that can be used in future studies to evaluate actinide covalency in compounds that contain transuranic elements.

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“…These differences in pre-edge areas can be understood as a direct reflection of the lower centrosymmetry of the individual iron centers in 1 due to the increased covalency of the oxo ligand that serves to further mediate iron 3d-4p mixing. 50–51 …”

Section: Results and Analysismentioning

confidence: 99%

High-Energy-Resolution Fluorescence-Detected X-ray Absorption of the Q Intermediate of Soluble Methane Monooxygenase

Castillo

Banerjee²,

Allpress³

et al. 2017

J. Am. Chem. Soc.

111

133

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Kα High-Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy (HERFD XAS) provides a powerful tool for overcoming the limitations of conventional XAS to identify the electronic structure and coordination environment of metalloprotein active sites. Herein, Fe Kα HERFD-XAS is applied to the diiron active site of soluble Methane Monooxygenase (sMMO) and to a series of high-valent diiron model complexes, including a “diamond core” [FeIV2(μ-O)2(L)2](ClO4)4] (3) and an “open core” [(O=FeIV–O–FeIV(OH)(L)2](ClO4)3 (4) (where, L = tris(3,5-dimethyl-4-methoxypyridyl-2-methyl)amine) (TPA*)). Pronounced differences in the HERFD XAS pre-edge energies and intensities are observed for the open vs. closed Fe2O2 cores in the model compounds. These differences are reproduced by time-dependent density functional theory (TDDFT) calculations and allow for the pre-edge energies and intensity to be directly correlated with the local active site geometric and electronic structure. A comparison of the model complex HERFD XAS data to that of MMOHQ (the key intermediate in methane oxidation) is supportive of an open core structure. Specifically, the large pre-edge area observed for MMOHQ may be rationalized by invoking an open core structure with a terminal FeIV=O motif, though further modulations of the core structure due to the protein environment cannot be ruled out. The present study, thus, motivates the need for additional experimental and theoretical studies to unambiguously assess the active site conformation of MMOHQ.

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Metal and Ligand K-Edge XAS of Organotitanium Complexes: Metal 4p and 3d Contributions to Pre-edge Intensity and Their Contributions to Bonding

Cited by 131 publications

References 44 publications

Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS₄²⁻(M = Cr, Mo, W) dianions

Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS₄²⁻(M = Cr, Mo, W) dianions

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

High-Energy-Resolution Fluorescence-Detected X-ray Absorption of the Q Intermediate of Soluble Methane Monooxygenase

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Metal and Ligand K-Edge XAS of Organotitanium Complexes: Metal 4p and 3d Contributions to Pre-edge Intensity and Their Contributions to Bonding

Cited by 131 publications

References 44 publications

Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS42−(M = Cr, Mo, W) dianions

Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS42−(M = Cr, Mo, W) dianions

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

High-Energy-Resolution Fluorescence-Detected X-ray Absorption of the Q Intermediate of Soluble Methane Monooxygenase

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Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS₄²⁻(M = Cr, Mo, W) dianions

Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M–S bonding for MS₄²⁻(M = Cr, Mo, W) dianions