Copper(I) and Copper(II) Complexes Possessing Cross-Linked Imidazole-Phenol Ligands: Structures and Dioxygen Reactivity
| Autor: | Arnold L. Rheingold, and Andreas D. Zuberbühler, Kenneth D. Karlin, Eunsuk Kim, Kaliappan Kamaraj, Lev N. Zakharov, Benedikt Galliker |
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| Rok vydání: | 2003 |
| Předmět: |
Models
Molecular Stereochemistry chemistry.chemical_element Crystal structure Crystallography X-Ray Biochemistry Medicinal chemistry Catalysis Electron Transport Complex IV chemistry.chemical_compound Colloid and Surface Chemistry Phenols Imidazole Moiety Reactivity (chemistry) Tetrahydrofuran Molecular Structure biology Imidazoles Active site General Chemistry Anisole Copper Oxygen chemistry biology.protein |
| Zdroj: | Journal of the American Chemical Society. 125:6028-6029 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja034263f |
| Popis: | Catalytic reduction of O2 to H2O, and coupling to membrane proton translocation, occurs at the heterobinuclear heme a3-CuB active site of cytochrome c oxidase. One of the CuB ligated histidines is cross-linked to a neighboring tyrosine (C-N bond; tyrosine C6 and histidine epsilon-nitrogen), and the protic residue of this cross-linked His-Tyr moiety is proposed to participate as both an electron and a proton donor in the catalytic dioxygen reduction event. To provide insight into the chemistry of such a moiety, we have synthesized and characterized tetra- and tridentate pyridylalkylamine chelate ligands {LN4OR and LN3OR (R = H or Me)}, which include an imidazole-phenol (or anisole) cross-link and their copper(I/II) complexes. [CuI(LN4OH)]B(C6F5)4 (1) reacts with dioxygen at -80 degrees C in THF, forming an unstable trans-mu-1,2-peroxodicopper(II)complex, which subsequently converts to a dimeric copper(II)-phenolate complex [{Cu(LN4O-)}2](B(C6F5)4)2 (5a). The close analogue [CuI(LN4OMe)]B(C6F5)4 (3) binds dioxygen reversibly at -80 degrees C in tetrahydrofuran. Stopped-flow kinetics of the reaction [CuI(LN3OH)]ClO4 (2) with O2 in CH2Cl2 indicate a steady formation of the purple dimeric product [{Cu(LN3O-)}2](ClO4)2 (5b), which has been analyzed in the temperature range from -40 to +20 degrees C, DeltaH = -9.6 (6) kJ mol-1, DeltaS = -168 (2) J mol-1 K-1 (k(-40 degrees C) = 1.05(4) x 106 and k(+20 degrees C) = 4.6(2) x 105 M-2 s-1). The X-ray crystal structures of 1, [CuII(LN3OH)(MeOH)(OClO3-)](ClO4) (4), 5a, and 5b are reported. |
| Databáze: | OpenAIRE |
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