Study On The Structure And Properties Of Clusters Constructed By M₁₃ Units

Due to the ultra-small size and controllable structure,the atomically precise metal nanoclusters have different properties from macroscopic substances,and have gradually become get more attentions in recent years.Therefore,because of its ultra-small size,exhibits molecular characteristics,different from the continuous energy band of plasmonic metal nanoparticles.In particular,for researcher nanoclusters with similar sizes but different core(or surface)structures often provide unique opportunities to explore the effects of core and surface structures without being affected by size.Research on the structure of nanoclusters found that the clusters can be regarded as being constructed from different structural units(such as Au₄,Au₁₁,M₁₃ units,etc.)through regulate the peripheral ligands or assembly.In this paper,based on previous works,choose bisphosphine ligands which have different chain lengths and cyclohexyl mercaptan to the protect units then synthesize Au₈Ag₅₇ and Au₁Ag₂₄ alloy nanoclusters,respectively,and phenylacetylene ligands were used to induce Au₈Ag₅₇ to transform into Au₈Ag₅₅.In addition,between Au₄Cu₄and Au₄Cu₅exist reversible transformation.The specific study content are as follows:1.Employing a bidentate phosphine ligand of 1,3-(bis-diphenylphosphine)propane and cyclohexyl mercaptan ligand to coprotect and synthesize a new alloy nanocluster—[Au₈Ag₅₇(Dppp)₄(C₆H₁₁S)₃₂Cl₂]Cl.Then adding phenylacetylene etching,the Au₈Ag₅₇nanocluster structure will be slightly reorganized,two chlorine atoms can separate a silver atom of the parent,respectively,and the vacant position filled by the thiol ligands.Finally,generate a new nanocluster[Au₈Ag₅₅(Dppp)₄(C₆H₁₁S)₃₄](BPh₄)₂.These clusters determined by X-ray single crystal diffraction(SC-XRD),and the composition further confirmed by electrospray mass spectrometry(ESI-MS),nuclear magnetic resonance(NMR)and X-ray photoelectron spectroscopy(XPS)measurements.The core of Au₈Ag₅₇ can be regarded as the Au₈Ag₄₁ metal core formed by the interpenetrating assembly of eight complete icosahedral Au₃Ag₁₀ units,form the three-dimensional structure,while Au₈Ag₅₅ consists of four complete Au@Ag₁₀Au₂ units and four incomplete Au@Ag₉Au₂ units assembled to form the metal core of Au₈Ag₃₉.The research content of this chapter is expected to further promote the research on the regulation of M₁₃ unit assemble and provide new directions for the influence of ligand exchange on the cluster structure.2.In this work,we synthesized a new silver-rich alloy nanocluster coprotected by 1,1-(bisdiphenylphosphine)methane and cyclohexyl mercaptan using the one-pot synthesis method,determined as[Au₁Ag₂₄(Dppm)₃(SR)₁₇]²⁺by SC-XRD and this was further confirmed by ESI-MS,TGA and XPS measurements.Different from the structure of[Au₁Ag₂₄(2,4-DMBT)₁₈]^-cluster with a closed Au₁Ag₁₂ icosahedron,which reported by the Osman M.Bakr group,the Au₁Ag₂₄ synthesized in this paper contains a special open Au₁Ag₁₂ icosahedral core.Interestingly,the number of free electrons is six,and the thermal stability is better.DFT calculation also confirmed the[Au₁Ag₂₄(Dppm)₃(SR)₁₇]²⁺has excellent oxidation resistance.This work combined the experiment and theory to explore the relation between structure and properties of clusters,provide new directions for subsequent researches.3.In this work,firstly,we synthesized a gold-copper alloy nanoclusters—[Au₄Cu₄(SAdm)₅(Dppm)₂]Br(Au₄Cu₄)through one-pot method,and then added some cyclohexyl mercaptan ligand,the Au₄Cu₄ cluster transform into a new cluster[Au₄Cu₅(C₆H₁₁S)₆(Dppm)₂](BPh₄)(Au₄Cu₅).At the same time,we also found that Au₄Cu₅ can be etched with adamantane mercaptan generate the Au₄Cu₄,along with the conversion of Cu₄(SAdm)₅ to Cu₅(C₆H₁₁S)₆motif,which means that between Au₄Cu₄ and Au₄Cu₅can emerge reversible conversion.And both changes can be tracked and monitored by UV-visible spectroscopy and electrospray mass spectrometry.Both Au₄Cu₄ and Au₄Cu₅ will produce photoluminescence in liquid and solid state.This work uses ligand engineering to realize the reversible conversion between Au₄Cu₅ and Au₄Cu₄,which provides a valuable reference for the follow-up study of Cu-S motif conversion.