Stepwise protonation and electron-transfer reduction of a primary copper-dioxygen adduct

Ryan L. Peterson; Jake W. Ginsbach; Ryan E. Cowley; Munzarin F. Qayyum; Richard A. Himes; Maxime A. Siegler; Cathy D. Moore; Britt Hedman; Keith O. Hodgson; Shunichi Fukuzumi; Edward I. Solomon; Kenneth D. Karlin

doi:10.1021/ja4065377

Stepwise protonation and electron-transfer reduction of a primary copper-dioxygen adduct

Ryan L. Peterson, Jake W. Ginsbach, Ryan E. Cowley, Munzarin F. Qayyum, Richard A. Himes, Maxime A. Siegler, Cathy D. Moore, Britt Hedman, Keith O. Hodgson, Shunichi Fukuzumi, Edward I. Solomon, Kenneth D. Karlin

Department of Chemistry & Nanoscience

Research output: Contribution to journal › Article › peer-review

70 Scopus citations

Abstract

The protonation-reduction of a dioxygen adduct with [LCu ^I][B(C₆F₅)₄], cupric superoxo complex [LCu^II(O₂^•-)]⁺ (1) (L = TMG₃tren (1,1,1-tris[2-[N²-(1,1,3,3-tetramethylguanidino) ]ethyl]amine)) has been investigated. Trifluoroacetic acid (HOAc_F) reversibly associates with the superoxo ligand in ([LCu^II(O ₂^•-)]⁺) in a 1:1 adduct [LCu ^II(O₂^•-)(HOAc_F)]⁺ (2), as characterized by UV-visible, resonance Raman (rR), nuclear magnetic resonance (NMR), and X-ray absorption (XAS) spectroscopies, along with density functional theory (DFT) calculations. Chemical studies reveal that for the binding of HOAc_F with 1 to give 2, K_eq = 1.2 × 10⁵ M^-1 (-130 C) and ΔH^o = -6.9(7) kcal/mol, ΔS^o = -26(4) cal mol^-1 K^-1). Vibrational (rR) data reveal a significant increase (29 cm^-1) in v_O-O (= 1149 cm^-1) compared to that known for [LCu ^II(O₂^•-)]⁺ (1). Along with results obtained from XAS and DFT calculations, hydrogen bonding of HOAc _F to a superoxo O-atom in 2 is established. Results from NMR spectroscopy of 2 at -120 C in 2-methyltetrahydrofuran are also consistent with 1/HOAc_F = 1:1 formulation of 2 and with this complex possessing a triplet (S = 1) ground state electronic configuration, as previously determined for 1. The pre-equilibrium acid association to 1 is followed by outer-sphere electron-transfer reduction of 2 by decamethylferrocene (Me₁₀Fc) or octamethylferrocene (Me₈Fc), leading to the products H ₂O₂, the corresponding ferrocenium salt, and [LCu ^II(OAc_F)]⁺. Second-order rate constants for electron transfer (k_et) were determined to be 1365 M^-1 s^-1 (Me₁₀Fc) and 225 M^-1 s^-1 (Me₈Fc) at -80 C. The (bio)chemical relevance of the proton-triggered reduction of the metal-bound dioxygen-derived fragment is discussed.

Original language	English
Pages (from-to)	16454-16467
Number of pages	14
Journal	Journal of the American Chemical Society
Volume	135
Issue number	44
DOIs	https://doi.org/10.1021/ja4065377
State	Published - 6 Nov 2013

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Peterson, R. L., Ginsbach, J. W., Cowley, R. E., Qayyum, M. F., Himes, R. A., Siegler, M. A., Moore, C. D., Hedman, B., Hodgson, K. O., Fukuzumi, S., Solomon, E. I., & Karlin, K. D. (2013). Stepwise protonation and electron-transfer reduction of a primary copper-dioxygen adduct. Journal of the American Chemical Society, 135(44), 16454-16467. https://doi.org/10.1021/ja4065377

@article{920a4bf28d3e4378a8083681dbedbbe8,

title = "Stepwise protonation and electron-transfer reduction of a primary copper-dioxygen adduct",

abstract = "The protonation-reduction of a dioxygen adduct with [LCu I][B(C6F5)4], cupric superoxo complex [LCuII(O2•-)]+ (1) (L = TMG3tren (1,1,1-tris[2-[N2-(1,1,3,3-tetramethylguanidino) ]ethyl]amine)) has been investigated. Trifluoroacetic acid (HOAcF) reversibly associates with the superoxo ligand in ([LCuII(O 2•-)]+) in a 1:1 adduct [LCu II(O2•-)(HOAcF)]+ (2), as characterized by UV-visible, resonance Raman (rR), nuclear magnetic resonance (NMR), and X-ray absorption (XAS) spectroscopies, along with density functional theory (DFT) calculations. Chemical studies reveal that for the binding of HOAcF with 1 to give 2, Keq = 1.2 × 105 M-1 (-130 C) and ΔHo = -6.9(7) kcal/mol, ΔSo = -26(4) cal mol-1 K-1). Vibrational (rR) data reveal a significant increase (29 cm-1) in vO-O (= 1149 cm-1) compared to that known for [LCu II(O2•-)]+ (1). Along with results obtained from XAS and DFT calculations, hydrogen bonding of HOAc F to a superoxo O-atom in 2 is established. Results from NMR spectroscopy of 2 at -120 C in 2-methyltetrahydrofuran are also consistent with 1/HOAcF = 1:1 formulation of 2 and with this complex possessing a triplet (S = 1) ground state electronic configuration, as previously determined for 1. The pre-equilibrium acid association to 1 is followed by outer-sphere electron-transfer reduction of 2 by decamethylferrocene (Me10Fc) or octamethylferrocene (Me8Fc), leading to the products H 2O2, the corresponding ferrocenium salt, and [LCu II(OAcF)]+. Second-order rate constants for electron transfer (ket) were determined to be 1365 M-1 s-1 (Me10Fc) and 225 M-1 s-1 (Me8Fc) at -80 C. The (bio)chemical relevance of the proton-triggered reduction of the metal-bound dioxygen-derived fragment is discussed.",

author = "Peterson, {Ryan L.} and Ginsbach, {Jake W.} and Cowley, {Ryan E.} and Qayyum, {Munzarin F.} and Himes, {Richard A.} and Siegler, {Maxime A.} and Moore, {Cathy D.} and Britt Hedman and Hodgson, {Keith O.} and Shunichi Fukuzumi and Solomon, {Edward I.} and Karlin, {Kenneth D.}",

year = "2013",

month = nov,

day = "6",

doi = "10.1021/ja4065377",

language = "English",

volume = "135",

pages = "16454--16467",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society",

number = "44",

}

TY - JOUR

T1 - Stepwise protonation and electron-transfer reduction of a primary copper-dioxygen adduct

AU - Peterson, Ryan L.

AU - Ginsbach, Jake W.

AU - Cowley, Ryan E.

AU - Qayyum, Munzarin F.

AU - Himes, Richard A.

AU - Siegler, Maxime A.

AU - Moore, Cathy D.

AU - Hedman, Britt

AU - Hodgson, Keith O.

AU - Fukuzumi, Shunichi

AU - Solomon, Edward I.

AU - Karlin, Kenneth D.

PY - 2013/11/6

Y1 - 2013/11/6

N2 - The protonation-reduction of a dioxygen adduct with [LCu I][B(C6F5)4], cupric superoxo complex [LCuII(O2•-)]+ (1) (L = TMG3tren (1,1,1-tris[2-[N2-(1,1,3,3-tetramethylguanidino) ]ethyl]amine)) has been investigated. Trifluoroacetic acid (HOAcF) reversibly associates with the superoxo ligand in ([LCuII(O 2•-)]+) in a 1:1 adduct [LCu II(O2•-)(HOAcF)]+ (2), as characterized by UV-visible, resonance Raman (rR), nuclear magnetic resonance (NMR), and X-ray absorption (XAS) spectroscopies, along with density functional theory (DFT) calculations. Chemical studies reveal that for the binding of HOAcF with 1 to give 2, Keq = 1.2 × 105 M-1 (-130 C) and ΔHo = -6.9(7) kcal/mol, ΔSo = -26(4) cal mol-1 K-1). Vibrational (rR) data reveal a significant increase (29 cm-1) in vO-O (= 1149 cm-1) compared to that known for [LCu II(O2•-)]+ (1). Along with results obtained from XAS and DFT calculations, hydrogen bonding of HOAc F to a superoxo O-atom in 2 is established. Results from NMR spectroscopy of 2 at -120 C in 2-methyltetrahydrofuran are also consistent with 1/HOAcF = 1:1 formulation of 2 and with this complex possessing a triplet (S = 1) ground state electronic configuration, as previously determined for 1. The pre-equilibrium acid association to 1 is followed by outer-sphere electron-transfer reduction of 2 by decamethylferrocene (Me10Fc) or octamethylferrocene (Me8Fc), leading to the products H 2O2, the corresponding ferrocenium salt, and [LCu II(OAcF)]+. Second-order rate constants for electron transfer (ket) were determined to be 1365 M-1 s-1 (Me10Fc) and 225 M-1 s-1 (Me8Fc) at -80 C. The (bio)chemical relevance of the proton-triggered reduction of the metal-bound dioxygen-derived fragment is discussed.

AB - The protonation-reduction of a dioxygen adduct with [LCu I][B(C6F5)4], cupric superoxo complex [LCuII(O2•-)]+ (1) (L = TMG3tren (1,1,1-tris[2-[N2-(1,1,3,3-tetramethylguanidino) ]ethyl]amine)) has been investigated. Trifluoroacetic acid (HOAcF) reversibly associates with the superoxo ligand in ([LCuII(O 2•-)]+) in a 1:1 adduct [LCu II(O2•-)(HOAcF)]+ (2), as characterized by UV-visible, resonance Raman (rR), nuclear magnetic resonance (NMR), and X-ray absorption (XAS) spectroscopies, along with density functional theory (DFT) calculations. Chemical studies reveal that for the binding of HOAcF with 1 to give 2, Keq = 1.2 × 105 M-1 (-130 C) and ΔHo = -6.9(7) kcal/mol, ΔSo = -26(4) cal mol-1 K-1). Vibrational (rR) data reveal a significant increase (29 cm-1) in vO-O (= 1149 cm-1) compared to that known for [LCu II(O2•-)]+ (1). Along with results obtained from XAS and DFT calculations, hydrogen bonding of HOAc F to a superoxo O-atom in 2 is established. Results from NMR spectroscopy of 2 at -120 C in 2-methyltetrahydrofuran are also consistent with 1/HOAcF = 1:1 formulation of 2 and with this complex possessing a triplet (S = 1) ground state electronic configuration, as previously determined for 1. The pre-equilibrium acid association to 1 is followed by outer-sphere electron-transfer reduction of 2 by decamethylferrocene (Me10Fc) or octamethylferrocene (Me8Fc), leading to the products H 2O2, the corresponding ferrocenium salt, and [LCu II(OAcF)]+. Second-order rate constants for electron transfer (ket) were determined to be 1365 M-1 s-1 (Me10Fc) and 225 M-1 s-1 (Me8Fc) at -80 C. The (bio)chemical relevance of the proton-triggered reduction of the metal-bound dioxygen-derived fragment is discussed.

UR - http://www.scopus.com/inward/record.url?scp=84887718844&partnerID=8YFLogxK

U2 - 10.1021/ja4065377

DO - 10.1021/ja4065377

M3 - Article

C2 - 24164682

AN - SCOPUS:84887718844

SN - 0002-7863

VL - 135

SP - 16454

EP - 16467

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 44

ER -

Stepwise protonation and electron-transfer reduction of a primary copper-dioxygen adduct

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