Synthesis And Characterization Of Thiol/Alkyne Protected Silver And/or Copper Nanoclusters

Metal nanoclusters are generally a transition state substance between a single atom or molecule and a macroblock,which composed of dozens to thousands of metal atoms.Based on the special size effect of nanoclusters,they have shown some unique optical and electrical properties in physical and chemical aspects and so on.As a result,metal nanoclusters have shown prefect application prospects in many fields.So far,a large number of gold,silver,copper and alloy nanoclusters with novel structures and unique properties have been prepared by adjusting the types of metal precursors and organic ligands and using different strategies.However,research on the mechanism of nanoclusters formation,especially the key role of organic ligands in the process of nanoclusters formation,has not been revealed yet.This thesis have studies the above issues from two aspects:the second chapter explores the effect of the amount of phosphine ligands on the structure and properties of the silver nanoclusters in the process of synthesis.The third chapter selects the special alkyne ligand and explores the effects and rules of different metal precursors silver,copper and silver-copper on the structure and coordination mode of metal nanoclusters.The main research work is as follows:1.Three completely different cases of silver nanoclusters co-protected by pentafluorothiol and 1,3-bisdiphenylphosphine propane were synthesized by adjusting the amount of phosphine ligand(Dppp)in the process of synthesis.They are Ag₄₄(SPh F₅)₂₄(Dppp)₆,Ag₃₂(SPh F₅)₁₈(Dppp)₅and Ag₁₈(SPh F₅)₉(Dppp)₅.By comparing of the structure of these three silver nanoclusters,it has been found that the number of nuclei and the symmetry of the structure of the silver nanoclusters continued to decrease with the increase of the amount of phosphine ligands.Obviously,the number of nuclei declined from 44 to 32 and18,but they all contain a common basic structure unit Ag₁₂icosahedron.However,the coordination modes of organic ligands and silver have been continuously enriched.For example,the bonding of HSPh F₅and Ag has changed from?₃coordination to?₃and?₂coordination and enriched again to?₃,?₂,and?₄coordination.Subsequently,the process of formation of three silver nanoclusters was tracked in ultraviolet and other methods.It was determined that the effect of the amount of phosphine ligand on the nucleation of the nanoclusters was generated after the addition of sodium borohydride as a reducing agent.2.Using the unique acetylene ligand^tBuC?CH^-as the main organic ligand,the silver nanocluster Ag₄₃(^tBuC?C)₂₄(CF₃SO₃)₈,the copper nanocluster Cu₅₃(^tBuC?C)₁₉(C₂H₃O₂)₁₀Cl₂and the silver-copper bimetal nanocluster Ag₈Cu₇(^tBuC?C)₁₂were successfully synthesized.And we characterized the structure and properties of the three metal nanoclusters.At the same time,it was analyzed and compared with tert-butylacetylene-protected seven cases of silver,copper,gold silver,and silver-copper nanoclusters that were reported in the literature.It revealed that tert-butylacetylene-stabilized silver nanoclusters uniformly appeared in?₃coordination mode.When copper or gold precursor was introduced,the structures of the silver-copper and gold-silver bimetallic nanoclusters and the coordination modes of tert-butylacetylene and metals remained unchanged,all of which were still?₃coordination.However,when the metal in the cluster was replaced with copper salt,the coordination mode of the tert-butylacetylene-stabilized copper nanoclusters appeared not only stable?₃coordination,but also?₂,?₄and?₅coordination.Furthermore,the catalytic properties of Ag₄₃(^tBuC?C)₂₄(CF₃SO₃)₈nanoclusters were investigated,and it was found that its surface ligands had a strong passivation effect in the catalytic reaction.