Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation.

Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation. Research Abstract Details 

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Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation. Abstract Text:

Eunsuk Kim,Jason Shearer,Shen Lu,Pierre ,Matthew E Helton,Susan Kaderli,Andreas D ,Kenneth D Karlin,

A new heme-peroxo-copper complex structural type with mu-eta2:eta2 peroxo ligation has been generated utilizing a heterobinucleating ligand with bis(2-(2-pyridyl)ethyl)amine tridentate chelate for copper. Oxygenation of [(2L)FeIICuI]+ (1) at -80 degrees C in CH2Cl2/6%EtCN, 1 (lambdamax, 426, 530 nm) produces [(2L)FeIII-(O22-)-CuII)]+ (3) (lambdamax, 419, 488, 544, 575 nm). Stopped-flow kinetic/spectroscopic probing reveals that a superoxo complex, [(2L)FeIII-(O2-)...CuI(NCEt)]+ (2) (lambdamax = 544 nm), initially forms, k1 = 5.23 +/- 0.09 x 104 M-1 s-1 (-105 degrees C). Subsequent intramolecular reaction of the copper(I) ion in 2 occurs with k2 = 2.74 +/- 0.04 x 101 s-1 (-105 degrees C), producing 3. Resonance Raman spectroscopy (rR) confirms the peroxo assignment for 3; nu(O-O) = 747 cm-1 (Delta(18O2) = -40 cm-1). In an 16O-18O mixed isotope experiment a single band is observed at 730 cm-1. The low nu(O-O) value and the absence of a splitting of the 730 cm-1 band are indicative of a symmetrical binding of the peroxide group in a side-on mu-eta2:eta2 geometry. This conclusion is supported by X-ray absorption spectroscopy on 3. Copper K-edge EXAFS indicates a five-coordinate metal center: 2 N, 2.028(7) A; 2 O, 1.898(7) A; 1 N, 2.171(12) A. An outer-sphere Fe scatterer is found at 3.62(1) A. The iron center K-edge EXAFS fits to either a five- or six-coordinate metal center: 4 N(pyrrole), approximately 2.1 A; 1,2 O, approximately 1.9 A. A preedge feature (Fe(1s) --> Fe(3d) transition) at 7113.2(2) eV resembles that obtained for a eta2-peroxo ferric heme complex, being weaker and at approximately 1.5 eV lower energy than those found in five-coordinate (P)FeIII-X (in C4v symmetry) complexes. Arguments based on rR properties of relevant peroxo compounds also effectively point to the copper(II) ion in 3 as being side-on bound, leading to the very low O-O stretching frequency observed in comparison to those of heme-peroxo species or heme-peroxo-copper complexes with a tetradentate copper chelate. These investigations derive from interest in establishing relevant and/or fundamental O2 chemistry at heme-copper centers, in relation to heme-copper oxidase active-site chemistry.

Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation. Publishing Authors By Initials

E Kim,J Shearer,S Lu,P ,ME Helton,S Kaderli,AD ,KD Karlin,

For similar investigative techniques: chemistry, analytical: scattering, radiation: spectrum analysis, raman research abstracts see: investigative techniques: chemistry, analytical: scattering, radiation: spectrum analysis, raman research

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Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation. Journal Published:

PUBLICATION TYPE: Research Support, U.S. Gov't,

Journal: Journal of the American Chemical Society

VOLUME: 126

Page Numbers: 12716-7

Journal Abbreviation: J. Am. Chem. Soc.

ISSN: 0002-7863

DAY: 13

MONTH: Oct

YEAR: 2004

Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation. Information

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LANGUAGE: eng

NlmUniqueID: 7503056

Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation. Keywords Mesh Terms:

KEYWORDS: Spectrum Analysis, Raman

MESH TERMS: chemistry

Chemical & Substance for Abstract: Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation. Information

Substance Name: Oxygen

Registry Number: 7782-44-7

Grant and Affiliation Information for Heme/Cu/O2 reactivity: change in FeIII-(O2 2-)-CuII unit peroxo binding geometry effected by tridentate copper chelation.

AFFILIATION: Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.

Country: United States

AGENCY: United States NIGMS

GRANT: GM 67447

ACRONYM: GM

MEDLINETA: J Am Chem Soc

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