Shape-Controlled Synthesis of Trimetallic Nanoclusters: Structure Elucidation and Properties Investigation

The shape-controlled synthesis of metal nanoclusters (NCs) with precise atomic arrangement is crucial for tailoring the properties. In this work, we successfully control the shape of alloy NCs by altering the dopants in the alloying processes. The shape of the spherical [Pt₁ Ag₂₄ (SPhMe₂ )₁₈ ] NC is maintained when [Au^I SR] is used as dopant. By contrast, the shape of Pt₁ Ag₂₄ is changed to be rodlike by alloying with [Au^I (PPh₃ )Br]. The structures of the trimetallic NCs were determined by X-ray crystallography and further confirmed by both DFT and far-IR measurements. The shape-preserved [Pt₁ Au_6.4 Ag_17.6 (SPhMe₂ )₁₈ ] NC is in a tristratified arrangement-[Pt(center)@Au/Ag(shell)@Ag(exterior)]-and is indeed the first X-ray crystal structure of thiolated trimetallic NCs. On the other hand, the resulting rodlike NC ([Pt₂ Au₁₀ Ag₁₃ (PPh₃ )₁₀ Br₇ ]) exhibits a high quantum yield (QY=14.7 %), which is in striking contrast to the weakly luminescent Pt₁ Ag₂₄ (QY=0.1 %, about 150-fold enhancement). In addition, the thermal stabilities of both trimetallic products are remarkably improved. This study presents a controllable strategy for synthesis of alloy NCs with different shapes (by alloying heteroatom complexes coordinated by different ligands), and may stimulate future work for a deeper understanding of the morphology (shape)-property correlation in NCs.