Shape-controlled Synthesis Of Tri-metallic Nanoclusters:Structure Elucidation And Properties Investigation

Atomically precise monolayer protected nanoclusters(NCs)have attracted increasing attention from both fundamental and practical aspects owing to their unique properties and wide applications in biology,catalysis,electronics and materials.So far,much effort has been devoted to synthesis of alloy NCs because of the enhanced properties.For example,our group recently developed a metal-exchange strategy to prepare the atomically precise alloy NCs,providing an efficient method to study the composition-property correlations.The atomically precise homometallic NCs are used as templates,and are doped with the heteroatom complexes to generate the target alloy NCs.Compared with monometallic NCs,the alloy NCs may show significantly enhanced optical,catalytic,and electrochemical properties.However,the previously reported alloy NCs only show changes in composition compared with the monometallic counterparts,and less effects on the properties of the NCs.We are motivated to pursue both composition and shape alterations;this would create new opportunities for tailoring the material properties.To achieve this goal,a major question is how to control the shape of the alloy NCs at the atomic level;this necessitates the development of new synthetic methods for alloy NCs.In the previously described metal-exchange method,the shape of the templating NCs is maintained by alloying with heteroatom complexes coordinated by the same ligands(exclusively thiolates in previous work).Therefore,it remains unknown whether the shape could be altered or not when the templating NCs are doped by heteroatom complexes with different ligands(such as,the very different M-SR and M-PR3 complexes,M= Au/Ag/Pt).In addition,whether or not the altered shape could induce the qualitative leap in properties deserves exploration.These studies will not only help us better understand the ligand effect in alloying processes in a confined environment(in the NC range),but also provide a reliable method to synthesize alloy NCs in an unprecedented shape-changing manner.Herein,we report an effective way to change the shape of NCs by alloying the same precursor—Pt1Ag24(protected by-SPhMe2)-with heteroatom complexes bearing different ligands.The contents are as follows:In this work,we successfully control the shape of alloy NCs by altering the dopants in the alloying processes.The shape of the spherical[PtiAg24(SPhMe2)18]NC is maintained when[AuSR]is used as dopant.By contrast,the shape of PtiAg24 is changed to be rod-like by alloying with[Au(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[Pt1Au6.4Ag17.6(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([Pt2Au10Ag13(PPh3)10Br7])exhibits a high quantum yield(QY=14.7%),which is in striking contrast to the weakly luminescent PtiAg24(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.