Probing Cu<sup>I</sup> in homogeneous catalysis using high-energy-resolution fluorescence-detected X-ray absorption spectroscopy

Walroth, R. C.; Uebler, Jacob W.; Lancaster, Kyle M.

doi:10.1039/c5cc01827g

Cited by 36 publications

(61 citation statements)

References 40 publications

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“…The additional pre-edge features arising from these three mechanisms can provide detailed insights into the identity and the electronic structure of the ligands. MLCT peaks have recently been observed in experimental Cu K-edge XAS spectra [9,26]. HERFD methods offer the possibility to resolve these weak peaks and thus have the potential to confirm the predictions made in this work and to make use of the additional electronic structure information encoded in Cu K-edge XAS spectra.…”

Section: Discussionsupporting

confidence: 62%

Section: Mo Analysis Of the Calculated Xas Spectra For Copper(i) Compmentioning

confidence: 64%

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Revisiting the Dependence of Cu K-Edge X-Ray Absorption Spectra on Oxidation State and Coordination Environment

Rudolph¹,

Jacob²

2018

Preprint

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X-ray absorption spectroscopy (XAS) at the Cu K-edge is an important tool for probing the properties of copper centers in transition metal chemistry and catalysis.However, the interpretation of experimental XAS spectra requires a detailed understanding of the dependence of spectroscopic features on the local geometric and electronic structure, which can be established by theoretical X-ray spectroscopy.Here, we present a systematic computational study of the Cu K-edge XAS spectra of selected Cu complexes based on time-dependent density-functional theory in combination with a molecular orbital analysis of the relevant transitions. For a series of Cu ammine model complexes as well as a comprehensive test set of 12 Cu(I) and 5 Cu(II) complexes, we revisit the dependence of the pre-edge region in Cu K-edge XAS spectra on oxidation state and coordination geometry. While our calculations confirm earlier experimental assignments, we can also reveal additional signatures of the ligand orbitals and identify the underlying orbital interactions.The comprehensive picture provided by this study will provide a reliable basis for the interpretation of in situ Cu K-edge XAS spectra of catalytic intermediates.2

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Section: Discussionsupporting

confidence: 62%

Section: Mo Analysis Of the Calculated Xas Spectra For Copper(i) Compmentioning

confidence: 64%

Revisiting the Dependence of Cu K-Edge X-Ray Absorption Spectra on Oxidation State and Coordination Environment

Rudolph¹,

Jacob²

2018

Preprint

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“…Thus, this peak is caused by a transition from the Cu core orbital to an unoccupied ligand orbital that acquires intensity through the admixture of Cu 4p contributions and can be classified as a metal-ligand charge transfer (MLCT) excitation. Such weak pre-edge peaks due to MLCT excitations to low-lying unoccupied ligand orbitals have recently been observed in HERFD-XAS spectra of Cu(I) complexes with bipyridine ligands 9. For the Cu(I) complexes E -H with coordination number three all calculated XAS spectra are shown inFig 5b and a comparisonhighlighting the contribution of the most relevant unoccupied MOs is shown inFig.…”

mentioning

confidence: 61%

“…X-ray spectroscopy provides a valuable tool for investigating the geometric and electronic structure of catalytic transition metal centers. [8][9][10] In particular, K-edge X-ray absorption spectroscopy (XAS) probes transitions from the metal 1s core orbital to unoccupied electronic states that depend both on the oxidation state of the metal center and the local coordination environment. 11,12 In the past years, high-energy resolution fluorescence detection XAS (HERFD-XAS) methods have been established [13][14][15][16][17] that remove the life-time broadening and thus reveal additional spectral features, in particular in the pre-edge region, which is due to transitions into chemically relevant low-lying unoccupied electronic states.…”

Section: Introductionmentioning

confidence: 99%

“…25, to the best of our knowledge these results have not been substantiated by computations so far. Even though for selected Cu complexes 9,26,27 and models of Cu centers in zeolites, 28,29 XAS spectra have been calculated and compared to experiment, a comprehensive understanding of the dependence of the features observed in Cu K-edge XAS spectra on the oxidation state and coordination geometry is still lacking (for a recent review, see Ref. 30).…”

Section: Introductionmentioning

confidence: 99%

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Revisiting the Dependence of Cu K-Edge X-ray Absorption Spectra on Oxidation State and Coordination Environment

Rudolph

Jacob

2018

Inorg. Chem.

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X-ray absorption spectroscopy (XAS) at the Cu K-edge is an important tool for probing the properties of copper centers in transition-metal chemistry and catalysis. However, the interpretation of experimental XAS spectra requires a detailed understanding of the dependence of spectroscopic features on the local geometric and electronic structure, which can be established by theoretical X-ray spectroscopy. Here, we present a systematic computational study of the Cu K-edge XAS spectra of selected Cu complexes based on time-dependent density-functional theory in combination with a molecular orbital analysis of the relevant transitions. For a series of Cu ammine model complexes as well as a comprehensive test set of 12 Cu(I) and 5 Cu(II) complexes, we revisit the dependence of the pre-edge region in Cu K-edge XAS spectra on oxidation state and coordination geometry. While our calculations confirm earlier experimental assignments, we can also reveal additional signatures of the ligand orbitals and identify the underlying orbital interactions. The comprehensive picture revealed by this study will provide a reliable basis for the interpretation of in situ Cu K-edge XAS spectra of catalytic intermediates.

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Enzyme‐Like Selectivity on Metalloporphyrin‐Catalyzed Oxidation by a Linear Homopolymer

et al. 2016

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The influence of linear homopolymers on manganese porphyrin-catalyzed oxidation of cyclohexene and phenol in solution was investigated. Cyclohexene was epoxidized in presence of poly(sodium acrylate)/poly(acrylic acid) (PAA) and H 2 O 2 , but the epoxide was the exclusive product only when the reaction was catalyzed by the manganese porphyrin. The regioselectivity of phenol catalytic oxidation in the para position increased up to 81 AE 14 % with PAA, however the same was not observed when PAA-substrate hydrogen bonding is hampered in oxidation of methoxybenzene. Unlike other bio-inspired systems the PAA polymer chain was not covalently bound to the metalloporphyrin, but it still promotes chemo-and regioselectivity. Catalytic data indicate active participation of the polymeric chain in epoxidation reaction in order to change the active oxidizing agent in the presence of the manganese porphyrin. The PAA chains act as a supramolecular directing agent, which binds phenol via hydrogen bond providing a favorable orientation for regioselective oxidation in the para position. The polymer chain dual role is unprecedented in enzyme-like catalysis with metalloporphyrin.[a] S.

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Probing Cu^I in homogeneous catalysis using high-energy-resolution fluorescence-detected X-ray absorption spectroscopy

Cited by 36 publications

References 40 publications

Revisiting the Dependence of Cu K-Edge X-Ray Absorption Spectra on Oxidation State and Coordination Environment

Revisiting the Dependence of Cu K-Edge X-Ray Absorption Spectra on Oxidation State and Coordination Environment

Revisiting the Dependence of Cu K-Edge X-ray Absorption Spectra on Oxidation State and Coordination Environment

Enzyme‐Like Selectivity on Metalloporphyrin‐Catalyzed Oxidation by a Linear Homopolymer

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Probing CuI in homogeneous catalysis using high-energy-resolution fluorescence-detected X-ray absorption spectroscopy

Cited by 36 publications

References 40 publications

Revisiting the Dependence of Cu K-Edge X-Ray Absorption Spectra on Oxidation State and Coordination Environment

Revisiting the Dependence of Cu K-Edge X-Ray Absorption Spectra on Oxidation State and Coordination Environment

Revisiting the Dependence of Cu K-Edge X-ray Absorption Spectra on Oxidation State and Coordination Environment

Enzyme‐Like Selectivity on Metalloporphyrin‐Catalyzed Oxidation by a Linear Homopolymer

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Probing Cu^I in homogeneous catalysis using high-energy-resolution fluorescence-detected X-ray absorption spectroscopy