Study On The Synthesis,Structure And Properties Of Au₂₈(SC₆H₁₁)₂₀ And Au_15.37Cu_16.63(SC₁₀H₁₅)₂₀ Clusters Protected By Thiol Ligands

Metal nanoclusters are also called molecular-like compounds,because the core size is in the range of 1-3 nm,which not only has molecular-like properties,but also has metal state behavior,making it a bridge between molecules and nanoparticles.Because of the special size range of the cluster,its physical and chemical properties are highly sensitive to atomic composition and structure;as long as they are slightly different,their physical and chemical properties will also change significantly.Nanoscientists are very interested in this discovery.However,in recent years,the synthetic methods for noble metal clusters have been limited to several classic methods that have been reported(ie,one-pot method,two-phase method,ligand exchange,metal exchange,inter-cluster reaction).Therefore,in order to explore the mystery of nanoclusters more deeply,exploring new synthetic methods has always been the research goal of researchers.Based on the current research status field of metal nanoclusters,we have conducted a thorough investigation of the reported literature,and after repeated experimental verification,we explored a new method of synthesizing metal nanoclusters.The specific synthesis content is as follows:1.A photo-induced transformation from[Au₂₃(S-c-C₆)₁₆]^-(TOA)⁺to Au₂₈(S-c-C₆)₂₀ nanocluster was first reported in this work.The[Au₂₃(S-c-C₆)₁₆]^-(TOA)⁺nanocluster is first excited to[Au₂₃(S-c-C₆)16]^·-(TOA)⁺by photons with energy higher than its E_g(E_g=HOMO-LUMO energy gap),and then,the negatively charged[Au₂₃(S-c-C₆)₁₆]^·-nanocluster was oxidized to the neutral state by transfering one electron to O₂.The unstable neutral cluster[Au₂₃(S-c-C₆)₁₆]⁰ obtained was decomposed into smaller nanocluster and finally reassembled into the Au₂₈(S-c-C₆)₂₀ nanocluster.We monitor the product through a series of test methods such as optical absorption spectroscopy to obtain the reaction mechanism of the cluster size change during the illumination process.2.Thiolated-alloy nanocluster Au_15.37Cu_16.63(S-Adm)₂₀((AuCu)₃₂ for short)has been synthesized.Single crystal X-ray crystallography(SC-XRD)proved this cluster contains a Au₁₄Cu₆ core which is composed of double superatom chains,and each superatom chain is composed of three Au₃Cu tetrahedrons sharing three vertices.Otherwise,two M₄(SR)₅(M=Au/Cu)motifs,four Cu(SR)₂ monomer staples and two SR molecules at the waist.These units together constitute a novel superatomic alloy cluster compound.Surprisingly,double superatom chains connect to each other only via two Au-Au bonds,which makes the kernel resemble a tunnel.Combining with DFT calculation and electronic structure analysis,it is further proved that(AuCu)₃₂nanocluster contains six 2e alloy superatomic Au₃Cu²⁺units.This work is the first report showing superatom units(CuAu₃²⁺)self-assembling to a hollow kernel maintain the superatom characteristic of metal nanoclusters,which enriches the fundamental knowledge on metal superatom clusters.In addition,the hollow structure may be promising in catalytic applications.