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. 2007 Jul;40(7):581-91.
doi: 10.1021/ar600060t. Epub 2007 May 2.

O2 and N2O activation by Bi-, Tri-, and tetranuclear Cu clusters in biology

Edward I Solomon  1 , Ritimukta Sarangi, Julia S Woertink, Anthony J Augustine, Jungjoo Yoon, Somdatta Ghosh
Affiliations

O2 and N2O activation by Bi-, Tri-, and tetranuclear Cu clusters in biology

Edward I Solomon et al. Acc Chem Res. 2007 Jul.

Abstract

Copper-cluster sites in biology exhibit unique spectroscopic features reflecting exchange coupling between oxidized Cu's and e (-) delocalization in mixed valent sites. These novel electronic structures play critical roles in O 2 binding and activation for electrophilic aromatic attack and H-atom abstraction, the 4e (-)/4H (+) reduction of O 2 to H 2O, and in the 2e (-)/2H (+) reduction of N 2O. These electronic structure/reactivity correlations are summarized below.

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Figures

Figure 1
Figure 1
Multinuclear Cu Sites in Biology
Figure 2
Figure 2
Electronic structure of (A) End-on Cu-O22− complex (B) End-on bridged [Cu2-O22−] complex and (C) Side-on bridged OxyHc.
Figure 3
Figure 3
(A) Absorption and (B) Resonance Raman spectra of {[(TMPA)Cu]2O2}2+ (end-on) (—), Cu[HB(3,5-i-Pr2pz)3]2(O2) (side-on) ( formula image) and {[LTMCHDCu]2O2} (bis-μ-oxo ( formula image)
Figure 4
Figure 4
(A)The reaction coordinate of O2 binding by Hc. View along the O-O (Top) and perpendicular to initial Cu2O2 plane (bottom). (B) Potential-energy surfaces for the interconversion of OxyHc and DeoxyHc in triplet and Singlet state. R:d(X-X) is the distance between the center of the O-O and Cu-Cu vectors. R:d(X-X) <~0.6 and >~0.6 represents symmetric and non-symmetric O2 coordination, respectively.
Figure 5
Figure 5
Molecular mechanism of Ty catalysis. The two possible structures of substrate bound oxy-T are expanded.
Figure 6
Figure 6
(A) Side-on peroxo (left), Bis-μ-Oxo (right) correlation (B) electronic structure correlation (C) FMO’s (ie. LUMO’s).
Figure 7
Figure 7
(A) Conversion of the side-on peroxide intermediate [Cu2(NO2-XYL)(O2)]2+ to [CuII2(NO2-XYL-O−)(OH)]2+. (B) & (C) Change in rR with time: loss of side-on peroxo stretch correlates with increase of C-O stretch.
Figure 8
Figure 8
(A) Reaction of Side-on peroxo {[(DBED)Cu]2O2}2+.(B) & (C) Change in rR with (tBu)2Ph(O)− coordination.
Figure 9
Figure 9
Geometry-optimized structures of the resting oxidized CuM and CuH sites in PHM.
Figure 10
Figure 10
Electronic structure of the CuIIM-OOH (A) and CuIIM-superoxo (B) species. Geometry-optimized structure (left), acceptor FMO (LUMO) (middle), rR spectra in νo-o region (right).
Figure 11
Figure 11
Summary of the 2e− (blue) and 1e− (red, green) reaction coordinates for the non-coupled binuclear Cu enzymes.
Figure 12
Figure 12
(A) Active site of the MCO’s (AO is shown here) (B) electronic structure of the TNC.
Figure 13
Figure 13
(A) Stopped-flow absorption showing the formation of NI, (B) RFQ-LT-MCD spectrum of NI, (C) VTMCD of NI, and (D) low temperature X-band EPR spectrum of NI compared to resting T2.
Figure 14
Figure 14
(A) Predicted and observed MCD signs for the two possible structures of NI and (B) ground and excited state MCD spectra of NI, where bands are grouped together according to their different temperature dependencies
Figure 15
Figure 15
MCO mechanism
Figure 16
Figure 16
(A) Crystal structure (PnN2OR) (B) Geometry optimized electronic structure
Figure 17
Figure 17
(A) Cu-K edge XAS spectrum of CuZ (black) simulated with 1CuII3/CuI and 3CuII/1CuI (B) EPR spectrum of CuZ from PnN2OR
Figure 18
Figure 18
(A) Backbonding interaction from fully reduced CuZ to N2O (B) N-O bond cleavage barrier of CuZ (red/grey), Cu2SH (black), H-bond assisted (blue).
Figure 19
Figure 19
N2OR reaction mechanism
See this image and copyright information in PMC

References

    1. Solomon EI, Sundaram UM, Machonkin TE. Multicopper Oxidases and Oxygenases. Chem Rev. 1996;96:2563–2605. - PubMed
    1. Pate JE, Cruse RW, Karlin KD, Solomon EI. Vibrational, electronic. and resonance Raman spectral studies of (Cu2(XYL-O-)O2)+, a copper(II) peroxide model complex of oxyhemocyanin. J Am Chem Soc. 1987;109:2624–30.
    1. Baldwin MJ, Ross PK, Pate JE, Tyeklár Z, Karlin KD, Solomon EI. Spectroscopic and Theoretical Studies of an End-On Peroxide-Bridged Coupled Binuclear Copper(II) Model Complex of Relevance to the Active Sites in Hemocyanin and Tyrosinase. J Am Chem Soc. 1991;113:8671–8679.
    1. Baldwin MJ, Root DE, Pate JE, Fujisawa K, Kitajima N, Solomon EI. Spectroscopic Studies of Side-on Peroxide-Bridged Binuclear Copper(II) Model Complexes of Relevance to Oxyhemocyanin and Oxytyrosinase. J Am Chem Soc. 1992;114:10421–10431.
    1. Metz M, Solomon EI. Dioxygen Binding to Deoxyhemocyanin: Electron Structure and Mechanism of the Spin Forbidden Two-Electron Reduction of O2. J Am Chem Soc. 2001;123:4938. - PubMed

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