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

76 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 - https://www.scopus.com/pages/publications/84887718844

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

Abstract

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