Issue 17, 2012

Electron transfer catalysis with monolayer protected Au25 clusters

Abstract

Au25L18 (L = S(CH2)2Ph) clusters were prepared and characterized. The resulting monodisperse clusters were reacted with bis(pentafluorobenzoyl) peroxide in dichloromethane to form Au25L18+ quantitatively. The kinetics and thermodynamics of the corresponding electron transfer (ET) reactions were characterized via electrochemistry and thermochemical calculations. Au25L18+ was used in homogeneous redox catalysis experiments with a series of sym-substituted benzoyl peroxides, including the above peroxide, bis(para-cyanobenzoyl) peroxide, dibenzoyl peroxide, and bis(para-methoxybenzoyl) peroxide. Peroxide dissociative ET was catalyzed using both the Au25L18/Au25L18 and the Au25L18+/Au25L18 redox couples as redox mediators. Simulation of the CV curves led to determination of the ET rate constant (kET) values for concerted dissociative ET to the peroxides. The ET free energy ΔG° could be estimated for all donor–acceptor combinations, leading to observation of a nice activation–driving force (log kETvs. ΔG°) relationship. Comparison with the kET obtained using a ferrocene-type donor with a formal potential similar to that of Au25L18/Au25L18 showed that the presence of the capping monolayer affects the ET rate rather significantly, which is attributed to the intrinsic nonadiabaticity of peroxide acceptors.

Graphical abstract: Electron transfer catalysis with monolayer protected Au25 clusters

Article information

Article type
Paper
Submitted
01 May 2012
Accepted
04 Jun 2012
First published
07 Jun 2012

Nanoscale, 2012,4, 5333-5342

Electron transfer catalysis with monolayer protected Au25 clusters

S. Antonello, M. Hesari, F. Polo and F. Maran, Nanoscale, 2012, 4, 5333 DOI: 10.1039/C2NR31066J

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