Size Growth of Au<sub>4</sub>Cu<sub>4</sub>: From Increased Nucleation to Surface Capping.
basic_science · Level V
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- Also identified by DOI 10.1021/acsnano.3c01238.
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Abstract
The size conversion of atomically precise metal nanoclusters is fundamental for elucidating structure-property correlations. In this study, copper salt (CuCl)-induced size growth from [Au<sub>4</sub>Cu<sub>4</sub>(Dppm)<sub>2</sub>(SAdm)<sub>5</sub>]<sup>+</sup> (abbreviated as <b>[Au</b><sub><b>4</b></sub><b>Cu</b><sub><b>4</b></sub><b>S</b><sub><b>5</b></sub><b>]</b><sup><b>+</b></sup>) to [Au<sub>4</sub>Cu<sub>6</sub>(Dppm)<sub>2</sub>(SAdm)<sub>4</sub>Cl<sub>3</sub>]<sup>+</sup> (abbreviated as <b>[Au</b><sub><b>4</b></sub><b>Cu</b><sub><b>6</b></sub><b>S</b><sub><b>4</b></sub><b>Cl</b><sub><b>3</b></sub><b>]</b><sup><b>+</b></sup>) (SAdmH = 1-adamantane mercaptan, Dppm = bis-(diphenylphosphino)methane) was investigated via experiments and density functional theory calculations. The <b>[Au</b><sub><b>4</b></sub><b>Cu</b><sub><b>4</b></sub><b>S</b><sub><b>5</b></sub><b>]</b><sup><b>+</b></sup> adopts a defective pentagonal bipyramid core structure with surface cavities, which could be easily filled with the sterically less hindered CuCl and CuSCy (i.e., core growth) (HSCy = cyclohexanethiol) but not the bulky CuSAdm. As long as the Au<sub>4</sub>Cu<sub>5</sub> framework is formed, ligand exchange or size growth occurs easily. However, owing to the compact pentagonal bipyramid core structure, the latter growth mode occurs only for the surface-capped [Au<sub>4</sub>Cu<sub>6</sub>(Dppm)<sub>2</sub>(SAdm)<sub>4</sub>Cl<sub>3</sub>]<sup>+</sup> structure (i.e., surface-capped size growth). A preliminary mechanistic study with density functional theory (DFT) calculations indicated that the overall conversion occurred via CuCl addition, core tautomerization, Cl migration, the second [CuCl] addition, and [CuCl]-[CuSR] exchange steps. And the [Au<sub>4</sub>Cu<sub>6</sub>(Dppm)<sub>2</sub>(SAdm)<sub>4</sub>Cl<sub>3</sub>]<sup>+</sup> alloy nanocluster exhibits aggregation-induced emission (AIE) with an absolute luminescence quantum yield of 18.01% in the solid state. This work sheds light on the structural transformation of Au-Cu alloy nanoclusters induced by Cu(I) and contributes to the knowledge base of metal-ion-induced size conversion of metal nanoclusters.