Chemistry and structural studies on the dioxygen-binding copper-1,2-dimethylimidazole system
- Johns Hopkins Univ., Baltimore, MD (United States)
- Daresby Lab., Warrington Cheshire (United Kingdom)
- Oregon Graduate Inst. of Science Technology, Portland, OR (United States)
Studies of copper complexes with the 1,2-dimethylimidazole (Me[sub 2]im) system have provided insights into the factors which control dioxygen (O[sub 2]) binding and activation in imidazole (histidine) ligated copper complexes and proteins. A two-coordinate complex [Cu(Me[sub 2]im)[sub 2]](PF[sub 6]) (1(PF[sub 6])) is formed by the reaction of 1,2-dimethylimidazole with [Cu(CH[sub 3]CN)[sub 4]](PF[sub 6]). Although 1 is unreactive toward O[sub 2] or CO, reaction with one additional molar equivalent of Me[sub 2]im yields a three-coordinate complex [Cu(Me[sub 2]im)[sub 3]](PF[sub 6])(2(PF[sub 6])) which reacts with O[sub 2](Cu/O[sub 2] = 2:1, manometry), producing the EPR silent dioxygen adduct, formulated as [Cu[sub 2](Me[sub 2]im)[sub 6](O[sub 2])][sup 2+] (3). The structure of 1 has been studied by X-ray crystallography; it crystallizes in the monoclinic space group C2/c with Z = 4, a = 14.877 (2) [angstrom], b = 15.950 (4) [angstrom], c = 6.931 (4) [angstrom], and [beta] = 108.54 (2)[degrees]. The linear two-coordinate Cu(I) structure is typical and contains crystallographically equivalent Cu-N(imid) distances of 1.865 [angstrom]. The structures of 2 and 3 have been studied by X-ray absorption spectroscopy, using imidazole group-fitting and full curved-wave multiple scattering analysis. Complex 2 is best fit by a T-shaped structure involving two short (1.89 [angstrom]) and one longer (2.08 [angstrom]) Cu-N(imid) distances. Absorption edge data confirm that the dioxygen complex 3 should be formulated as a Cu(II)-peroxo species. The EXAFS of 3 can be fit by either of two models, A and B. 50 refs., 9 figs., 3 tabs.
- OSTI ID:
- 5154464
- Journal Information:
- Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:24; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
AZOLES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COMPLEXES
COPPER COMPLEXES
CRYSTALLOGRAPHY
DATA
DIFFRACTION
ELEMENTS
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
IMIDAZOLES
INFORMATION
LIGANDS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PEROXIDES
SCATTERING
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
X-RAY DIFFRACTION