TY - JOUR
T1 - Heme-copper/dioxygen adduct formation relevant to cytochrome c oxidase
T2 - Spectroscopic characterization of [(6L)FeIII-(O 22-)-CuII]+
AU - Ghiladi, Reza A.
AU - Huang, Hong Wei
AU - Moënne-Loccoz, Pierre
AU - Stasser, Jay
AU - Blackburn, Ninian J.
AU - Woods, Amina S.
AU - Cotter, Robert J.
AU - Incarvito, Christopher D.
AU - Rheingold, Arnold L.
AU - Karlin, Kenneth D.
N1 - Funding Information:
Acknowledgements We are grateful to the National Institutes of Health (K.D.K., GM60353; R.J.C., GM54882; P.M.-L., GM18865) for support of this research.
PY - 2005/1
Y1 - 2005/1
N2 - In the further development and understanding of heme-copper dioxygen reactivity relevant to cytochrome c oxidase O2-reduction chemistry, we describe a high-spin, five-coordinate dioxygen (peroxo) adduct of an iron(II)-copper(I) complex, [(6L)FeIICu I](BArF20) (1), where 6L is a tetraarylporphyrinate with a tethered tris(2-pyridylmethyl)amine chelate for copper. Reaction of 1 with O2 in MeCN affords a remarkably stable [t1/2 (rt; MeCN)≈60 min] adduct, [(6L)Fe III-(O22-)-CuII]+ (2) [EPR silent; λmax = 418 (Soret), 561 nm], formulated as a peroxo complex based on manometry (1:O2 = 1:1; spectrophotometric titration, -40°C, MeCN), mass spectrometry {MALDI-TOF-MS: 16O2, m/z 1191 ([(6L)FeIII-( 16O22-)-CuII]+); 18O2, m/z 1195}, and resonance Raman spectroscopy (νv(O-O) = 788 cm-1; Δ16O 2/18O2 = 44 cm-1; Δ16O2/16/18O2 = 22 cm -1). 1H and 2H NMR spectroscopy (-40°C, MeCN) reveals that 2 is the first heme-copper peroxo complex which is high-spin, with downfield-shifted pyrrole resonances (δpyrrole = 75 ppm, s, br) and upfield shifted peaks at δ = -22, -35, and -40 ppm, similar to the pattern observed for the μ-oxo complex [(6L)Fe III-O-CuII](BArF) (3) (known S = 2 system, antiferromagnetically coupled high-spin FeIII and CuII). The corresponding magnetic moment measurement (Evans method, CD3CN, -40°C) also confirms the S = 2 spin state, with μB = 4.9. Structural insights were obtained from X-ray absorption spectroscopy, showing Fe-O (1.83 Å) and Cu-O (1.882 Å) bonds, and an Fe...Cu distance of 3.35(2) Å, suggestive of a μ-1,2-peroxo ligand present in 2. The reaction of 2 with cobaltocene gives 3, differing from the observed full reduction seen with other heme-Cu peroxo complexes. Finally, thermal decomposition of 2 yields 3, with concomitant release of 0.5 mol O2 per mol 2, as confirmed quantitatively by an alkaline pyrogallol dioxygen scavenging solution.
AB - In the further development and understanding of heme-copper dioxygen reactivity relevant to cytochrome c oxidase O2-reduction chemistry, we describe a high-spin, five-coordinate dioxygen (peroxo) adduct of an iron(II)-copper(I) complex, [(6L)FeIICu I](BArF20) (1), where 6L is a tetraarylporphyrinate with a tethered tris(2-pyridylmethyl)amine chelate for copper. Reaction of 1 with O2 in MeCN affords a remarkably stable [t1/2 (rt; MeCN)≈60 min] adduct, [(6L)Fe III-(O22-)-CuII]+ (2) [EPR silent; λmax = 418 (Soret), 561 nm], formulated as a peroxo complex based on manometry (1:O2 = 1:1; spectrophotometric titration, -40°C, MeCN), mass spectrometry {MALDI-TOF-MS: 16O2, m/z 1191 ([(6L)FeIII-( 16O22-)-CuII]+); 18O2, m/z 1195}, and resonance Raman spectroscopy (νv(O-O) = 788 cm-1; Δ16O 2/18O2 = 44 cm-1; Δ16O2/16/18O2 = 22 cm -1). 1H and 2H NMR spectroscopy (-40°C, MeCN) reveals that 2 is the first heme-copper peroxo complex which is high-spin, with downfield-shifted pyrrole resonances (δpyrrole = 75 ppm, s, br) and upfield shifted peaks at δ = -22, -35, and -40 ppm, similar to the pattern observed for the μ-oxo complex [(6L)Fe III-O-CuII](BArF) (3) (known S = 2 system, antiferromagnetically coupled high-spin FeIII and CuII). The corresponding magnetic moment measurement (Evans method, CD3CN, -40°C) also confirms the S = 2 spin state, with μB = 4.9. Structural insights were obtained from X-ray absorption spectroscopy, showing Fe-O (1.83 Å) and Cu-O (1.882 Å) bonds, and an Fe...Cu distance of 3.35(2) Å, suggestive of a μ-1,2-peroxo ligand present in 2. The reaction of 2 with cobaltocene gives 3, differing from the observed full reduction seen with other heme-Cu peroxo complexes. Finally, thermal decomposition of 2 yields 3, with concomitant release of 0.5 mol O2 per mol 2, as confirmed quantitatively by an alkaline pyrogallol dioxygen scavenging solution.
KW - Dioxygen adduct
KW - Heme-copper
KW - Iron(II)-copper(I) complex
KW - Mass spectrometry
KW - Model compound
KW - Peroxo complex
KW - Resonance Raman spectroscopy
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U2 - 10.1007/s00775-004-0609-1
DO - 10.1007/s00775-004-0609-1
M3 - Article
C2 - 15583964
AN - SCOPUS:19944430917
SN - 0949-8257
VL - 10
SP - 63
EP - 77
JO - Journal of Biological Inorganic Chemistry
JF - Journal of Biological Inorganic Chemistry
IS - 1
ER -