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Analytical Chemistry

Cluster Size Controls Dioxygen Binding

Finding may help scientists understand how nanocrystalline gold activates dioxygen

by Mitch Jacoby
May 28, 2012 | A version of this story appeared in Volume 90, Issue 22

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Credit: JACS
The size of gold clusters determines whether O2 binds in a bridging or nonbridging configuration.
Depictions of 5 dioxygen-gold clusters.
Credit: JACS
The size of gold clusters determines whether O2 binds in a bridging or nonbridging configuration.

The manner in which oxygen binds to gold clusters depends on the number of atoms in the cluster, according to a pair of studies conducted independently. The findings may help researchers understand the surprising catalytic activity exhibited by gold in nanocrystalline form. Considered chemically inactive for ages, gold has demonstrated its catalytic prowess repeatedly in the past decade. Yet it has remained unclear how gold nanostructures bind O2, which activates the molecule for gold’s most studied catalytic trick—oxidation. Now, two research teams have independently determined through experimental and computational methods that anionic gold clusters with two, four, or six gold atoms bind O2 in a nonbridging superoxo (end-on) fashion. Larger anionic clusters with 10, 12, and 14 gold atoms bind O2 in a bridging peroxo configuration. O2Au8 can adopt either of the structures, which differ only slightly in energy. One of the teams was led by André Fielicke of the Fritz Haber Institute in Berlin (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201108958). The other study was led by Lai-Sheng Wang of Brown University and Xiao Cheng Zeng of the University of Nebraska, Lincoln (J. Am. Chem. Soc., DOI: 10.1021/ja302902p).

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