Isomerism in Au–Ag Alloy Nanoclusters: Structure
Determination and Enantioseparation of [Au<sub>9</sub>Ag<sub>12</sub>(SR)<sub>4</sub>(dppm)<sub>6</sub>X<sub>6</sub>]<sup>3+</sup>
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Abstract
Revealing structural isomerism in
a nanocluster remains significant but challenging. Herein, we have
obtained a pair of structural isomers, [Au<sub>9</sub>Ag<sub>12</sub>(SR)<sub>4</sub>(dppm)<sub>6</sub>X<sub>6</sub>]<sup>3+</sup>-C and [Au<sub>9</sub>Ag<sub>12</sub>(SR)<sub>4</sub>(dppm)<sub>6</sub>X<sub>6</sub>]<sup>3+</sup>-Ac
[dppm = bis(diphenyphosphino)methane; HSR = 1-adamantanethiol/<i>tert</i>-butylmercaptan; X = Br/Cl; C stands for one of the
structural isomers being chiral; Ac stands for another being achiral],
that show different structures as well as different chiralities. These
structures are determined by single-crystal X-ray diffraction and
further confirmed by high-resolution electrospray ionization mass
spectrometry. On the basis of the isomeric structures, the most important
finding is the different arrangements of the Au<sub>5</sub>Ag<sub>8</sub>@Au<sub>4</sub> metal core, leading to changes in the overall
shape of the cluster, which is responsible for structural isomerism.
Meanwhile, the two enantiomers of [Au<sub>9</sub>Ag<sub>12</sub>(SR)<sub>4</sub>(dppm)<sub>6</sub>X<sub>6</sub>]<sup>3+</sup>-C are separated by high-performance liquid chromatography.
Our work will contribute to a deeper understanding of the structural
isomerism in noble-metal nanoclusters and enrich the chiral nanocluster
