Dioxygen reactivity of copper and heme-copper complexes possessing an imidazole-phenol cross-link

Eunsuk Kim, Kaliappan Kamaraj, Benedikt Galliker, Nick D. Rubie, Pierre Moenne-Loccoz, Susan Kaderli, Andreas D. Zuberbühler, Kenneth D. Karlin

Research output: Contribution to journalArticle

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Abstract

Recent spectroscopic, kinetics, and structural studies on cytochrome c oxidases (CcOs) suggest that the histidine-tyrosine cross-link at the heme a3-CuB binuclear active site plays a key role in the reductive O2-cleavage process. In this report, we describe dioxygen reactivity of copper and heme/Cu assemblies in which the imidazole-phenol moieties are employed as a part of copper ligand LN4OH (2-{4-[2-(bis-pyridin-2-ylmethyl-amino)-ethyl]-imidazol-1-yl}-4,6-di- tert-butyl-phenol). Stopped-flow kinetic studies reveal that low-temperature oxygenation of [CuI(LN4OH)]+ (1) leads to rapid formation of a copper-superoxo species [CuII(LN4OH) (O2 -)]+ (1a), which further reacts with 1 to form the 2:1 Cu:O2 adduct, peroxo complex [{CuII(L N4OH)}2(O2 2-)]2+ (1b). Complex 1b is also short-lived, and a dimer Cu(II)-phenolate complex [Cu II(LN4O-)]2 2+ (1c) eventually forms as a final product in the later stage of the oxygenation reaction. Dioxygen reactivities of 1 and its anisole analogue [Cu I(LN4OMe)]+ (2) in the presence of a heme complex (F8)FeII (3) (F8 = tetrakis(2,6,- difluorotetraphenyl)-porphyrinate) are also described. Spectroscopic investigations including UV-vis, 1H and 2H NMR, EPR, and resonance Raman spectroscopies along with spectrophotometric titration reveal that low-temperature oxygenation of 1/3 leads to formation of a heme-peroxo-copper species [(F8)FeIII-(O2 2-)-CuII(LN4OH)]+ (4), ν(O-O) = 813 cm-1. Complex 4 is an S = 2 spin system with strong antiferromagnetic coupling between high-spin iron(III) and copper(II) through a bridging peroxide ligand. A very similar complex [(F 8)FeIII-(O2 2-)-Cu II(LN4OMe)]+ (5) (ν(O-O) = 815 cm-1) can be generated by utilizing the anisole compound 2, which indicates that the cross-linked phenol moiety in 4 does not interact with the bridging peroxo group between heme and copper. This investigation thus reveals that a stable heme-peroxo-copper species can be generated even in the presence of an imidazole-phenol group (i.e., possible electron/proton donor source) in close proximity. Future studies are needed to probe key factors that can trigger the reductive O-O cleavage in CcO model compounds.

Original languageEnglish (US)
Pages (from-to)1238-1247
Number of pages10
JournalInorganic Chemistry
Volume44
Issue number5
DOIs
StatePublished - Mar 7 2005

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Phenol
Heme
imidazoles
phenols
Copper
reactivity
Oxygen
copper
Oxygenation
oxygenation
anisole
cleavage
Ligands
ligands
Kinetics
histidine
tyrosine
oxidase
cytochromes
Peroxides

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Dioxygen reactivity of copper and heme-copper complexes possessing an imidazole-phenol cross-link. / Kim, Eunsuk; Kamaraj, Kaliappan; Galliker, Benedikt; Rubie, Nick D.; Moenne-Loccoz, Pierre; Kaderli, Susan; Zuberbühler, Andreas D.; Karlin, Kenneth D.

In: Inorganic Chemistry, Vol. 44, No. 5, 07.03.2005, p. 1238-1247.

Research output: Contribution to journalArticle

Kim, E, Kamaraj, K, Galliker, B, Rubie, ND, Moenne-Loccoz, P, Kaderli, S, Zuberbühler, AD & Karlin, KD 2005, 'Dioxygen reactivity of copper and heme-copper complexes possessing an imidazole-phenol cross-link', Inorganic Chemistry, vol. 44, no. 5, pp. 1238-1247. https://doi.org/10.1021/ic048907b
Kim, Eunsuk ; Kamaraj, Kaliappan ; Galliker, Benedikt ; Rubie, Nick D. ; Moenne-Loccoz, Pierre ; Kaderli, Susan ; Zuberbühler, Andreas D. ; Karlin, Kenneth D. / Dioxygen reactivity of copper and heme-copper complexes possessing an imidazole-phenol cross-link. In: Inorganic Chemistry. 2005 ; Vol. 44, No. 5. pp. 1238-1247.
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title = "Dioxygen reactivity of copper and heme-copper complexes possessing an imidazole-phenol cross-link",
abstract = "Recent spectroscopic, kinetics, and structural studies on cytochrome c oxidases (CcOs) suggest that the histidine-tyrosine cross-link at the heme a3-CuB binuclear active site plays a key role in the reductive O2-cleavage process. In this report, we describe dioxygen reactivity of copper and heme/Cu assemblies in which the imidazole-phenol moieties are employed as a part of copper ligand LN4OH (2-{4-[2-(bis-pyridin-2-ylmethyl-amino)-ethyl]-imidazol-1-yl}-4,6-di- tert-butyl-phenol). Stopped-flow kinetic studies reveal that low-temperature oxygenation of [CuI(LN4OH)]+ (1) leads to rapid formation of a copper-superoxo species [CuII(LN4OH) (O2 -)]+ (1a), which further reacts with 1 to form the 2:1 Cu:O2 adduct, peroxo complex [{CuII(L N4OH)}2(O2 2-)]2+ (1b). Complex 1b is also short-lived, and a dimer Cu(II)-phenolate complex [Cu II(LN4O-)]2 2+ (1c) eventually forms as a final product in the later stage of the oxygenation reaction. Dioxygen reactivities of 1 and its anisole analogue [Cu I(LN4OMe)]+ (2) in the presence of a heme complex (F8)FeII (3) (F8 = tetrakis(2,6,- difluorotetraphenyl)-porphyrinate) are also described. Spectroscopic investigations including UV-vis, 1H and 2H NMR, EPR, and resonance Raman spectroscopies along with spectrophotometric titration reveal that low-temperature oxygenation of 1/3 leads to formation of a heme-peroxo-copper species [(F8)FeIII-(O2 2-)-CuII(LN4OH)]+ (4), ν(O-O) = 813 cm-1. Complex 4 is an S = 2 spin system with strong antiferromagnetic coupling between high-spin iron(III) and copper(II) through a bridging peroxide ligand. A very similar complex [(F 8)FeIII-(O2 2-)-Cu II(LN4OMe)]+ (5) (ν(O-O) = 815 cm-1) can be generated by utilizing the anisole compound 2, which indicates that the cross-linked phenol moiety in 4 does not interact with the bridging peroxo group between heme and copper. This investigation thus reveals that a stable heme-peroxo-copper species can be generated even in the presence of an imidazole-phenol group (i.e., possible electron/proton donor source) in close proximity. Future studies are needed to probe key factors that can trigger the reductive O-O cleavage in CcO model compounds.",
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T1 - Dioxygen reactivity of copper and heme-copper complexes possessing an imidazole-phenol cross-link

AU - Kim, Eunsuk

AU - Kamaraj, Kaliappan

AU - Galliker, Benedikt

AU - Rubie, Nick D.

AU - Moenne-Loccoz, Pierre

AU - Kaderli, Susan

AU - Zuberbühler, Andreas D.

AU - Karlin, Kenneth D.

PY - 2005/3/7

Y1 - 2005/3/7

N2 - Recent spectroscopic, kinetics, and structural studies on cytochrome c oxidases (CcOs) suggest that the histidine-tyrosine cross-link at the heme a3-CuB binuclear active site plays a key role in the reductive O2-cleavage process. In this report, we describe dioxygen reactivity of copper and heme/Cu assemblies in which the imidazole-phenol moieties are employed as a part of copper ligand LN4OH (2-{4-[2-(bis-pyridin-2-ylmethyl-amino)-ethyl]-imidazol-1-yl}-4,6-di- tert-butyl-phenol). Stopped-flow kinetic studies reveal that low-temperature oxygenation of [CuI(LN4OH)]+ (1) leads to rapid formation of a copper-superoxo species [CuII(LN4OH) (O2 -)]+ (1a), which further reacts with 1 to form the 2:1 Cu:O2 adduct, peroxo complex [{CuII(L N4OH)}2(O2 2-)]2+ (1b). Complex 1b is also short-lived, and a dimer Cu(II)-phenolate complex [Cu II(LN4O-)]2 2+ (1c) eventually forms as a final product in the later stage of the oxygenation reaction. Dioxygen reactivities of 1 and its anisole analogue [Cu I(LN4OMe)]+ (2) in the presence of a heme complex (F8)FeII (3) (F8 = tetrakis(2,6,- difluorotetraphenyl)-porphyrinate) are also described. Spectroscopic investigations including UV-vis, 1H and 2H NMR, EPR, and resonance Raman spectroscopies along with spectrophotometric titration reveal that low-temperature oxygenation of 1/3 leads to formation of a heme-peroxo-copper species [(F8)FeIII-(O2 2-)-CuII(LN4OH)]+ (4), ν(O-O) = 813 cm-1. Complex 4 is an S = 2 spin system with strong antiferromagnetic coupling between high-spin iron(III) and copper(II) through a bridging peroxide ligand. A very similar complex [(F 8)FeIII-(O2 2-)-Cu II(LN4OMe)]+ (5) (ν(O-O) = 815 cm-1) can be generated by utilizing the anisole compound 2, which indicates that the cross-linked phenol moiety in 4 does not interact with the bridging peroxo group between heme and copper. This investigation thus reveals that a stable heme-peroxo-copper species can be generated even in the presence of an imidazole-phenol group (i.e., possible electron/proton donor source) in close proximity. Future studies are needed to probe key factors that can trigger the reductive O-O cleavage in CcO model compounds.

AB - Recent spectroscopic, kinetics, and structural studies on cytochrome c oxidases (CcOs) suggest that the histidine-tyrosine cross-link at the heme a3-CuB binuclear active site plays a key role in the reductive O2-cleavage process. In this report, we describe dioxygen reactivity of copper and heme/Cu assemblies in which the imidazole-phenol moieties are employed as a part of copper ligand LN4OH (2-{4-[2-(bis-pyridin-2-ylmethyl-amino)-ethyl]-imidazol-1-yl}-4,6-di- tert-butyl-phenol). Stopped-flow kinetic studies reveal that low-temperature oxygenation of [CuI(LN4OH)]+ (1) leads to rapid formation of a copper-superoxo species [CuII(LN4OH) (O2 -)]+ (1a), which further reacts with 1 to form the 2:1 Cu:O2 adduct, peroxo complex [{CuII(L N4OH)}2(O2 2-)]2+ (1b). Complex 1b is also short-lived, and a dimer Cu(II)-phenolate complex [Cu II(LN4O-)]2 2+ (1c) eventually forms as a final product in the later stage of the oxygenation reaction. Dioxygen reactivities of 1 and its anisole analogue [Cu I(LN4OMe)]+ (2) in the presence of a heme complex (F8)FeII (3) (F8 = tetrakis(2,6,- difluorotetraphenyl)-porphyrinate) are also described. Spectroscopic investigations including UV-vis, 1H and 2H NMR, EPR, and resonance Raman spectroscopies along with spectrophotometric titration reveal that low-temperature oxygenation of 1/3 leads to formation of a heme-peroxo-copper species [(F8)FeIII-(O2 2-)-CuII(LN4OH)]+ (4), ν(O-O) = 813 cm-1. Complex 4 is an S = 2 spin system with strong antiferromagnetic coupling between high-spin iron(III) and copper(II) through a bridging peroxide ligand. A very similar complex [(F 8)FeIII-(O2 2-)-Cu II(LN4OMe)]+ (5) (ν(O-O) = 815 cm-1) can be generated by utilizing the anisole compound 2, which indicates that the cross-linked phenol moiety in 4 does not interact with the bridging peroxo group between heme and copper. This investigation thus reveals that a stable heme-peroxo-copper species can be generated even in the presence of an imidazole-phenol group (i.e., possible electron/proton donor source) in close proximity. Future studies are needed to probe key factors that can trigger the reductive O-O cleavage in CcO model compounds.

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