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Issue 4, 2013
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Three coordinate models for the binuclear CuA electron-transfer site

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Abstract

Truly three coordinate CuA synthetic models were developed by employing bulky N-heterocyclic carbene ligands along with simple C3 and C4 dithiolate linkers to emulate the role of histidine and cysteine ligands at trigonal copper sites. The reduced [CuICuI] models [NHC]Cu–S(CH2)nS–Cu[NHC] (n = 3 (3), 4 (4)) were characterized by NMR and X-ray crystallography. The structure of the reduced model with the C3 linker closely mimics the low coordinate, trigonal environment at the reduced dinuclear CuA site while the C4 linker resulted in an “open” solid state structure with two coordinate Cu centers. Oxidized species 3++++ and 4+++ were observed by UV-vis and EPR spectroscopy upon the addition of [Cp2Fe]+ to 3 and 4, generating spectroscopic features similar to those of the dinuclear [Cu1.5Cu1.5]+ CuA resting state. Key spectroscopic features of 3++++ and 4+++ are low energy intervalence charge transfer bands centered near 1150 nm and EPR spectra indicating delocalization of the unpaired e among two Cu centers. Electrochemistry of the oxidized [Cu2S2]+ models reveals reduction potentials (E1/2 = 0.11 V (3++++); 0.36 V (4+++) vs. NHE) similar to the CuA site in CcO (E1/2 = 0.22–0.30 V vs. NHE).

Graphical abstract: Three coordinate models for the binuclear CuA electron-transfer site

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Publication details

The article was received on 07 Nov 2012, accepted on 30 Jan 2013 and first published on 01 Feb 2013


Article type: Edge Article
DOI: 10.1039/C3SC21936D
Citation: Chem. Sci., 2013,4, 1786-1792
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    Three coordinate models for the binuclear CuA electron-transfer site

    S. Zhang and T. H. Warren, Chem. Sci., 2013, 4, 1786
    DOI: 10.1039/C3SC21936D

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