Synthesis,Structure And Properties Of Coinage Metal Nanoclusters Based On Organic Amine Ligands

Organic-capped coinage metal nanoclusters have attracted much attention in recent years owing to their atomically precise nature and unique properties.Because of the quantum-size and surface effects,nanoclusters have been exhibiting potential applications in catalysis,biomedicine,optical,and sensing.As the outmost surface structures,the protecting ligands are crucial to the core structures,properties and applications of the whole nanoclusters.In order to enrich the structural diversity of metal nanoclusters,this dissertation focuses on increasing the type of the protecting ligands and utilizing the polydentate amine ligands to synthesize novel nanoclusters.On the basis of the structure determination and structural comparisons between homoleptic amine and multiple ligands-protected nanoclusters,we find that surface-capping agents play important roles in forming novel core structure and observe the coordination modes of the amine ligands.We utilized a new polydentate ligand(2,2’-Dipyridylamine)as a protection and synthesized a series of structurally defined amine-procted nanoclusters(Ag44Au5,Ag55Au6,and Ag21Au1)for the first time.It was found that polydentate amine was versatile and could proctect the nanoclusters with various coordination modes.The Ag44Aus and Ag55Au6 clusters consisted of three and four(AuAg)13 units sharing vertex atoms respectively,which enriched the type of cluster nanoclusters.Additionally,we investigate the difference of optical properties between alloy cluster Ag55Au6 and homometallic analogue Ag61,and we understood the influence of the doped atoms on the properties at atom level.In order to improve the diversity of cluster structures and properties,we synthesized a series of amine and phosphine or chloride co-protected alloy nanoclusters(Ag18Au18,Ag34Au8,Ag5Au10).It was worth mentioning that chloride and phosphine ligands were significant for improving symmetry of clusters and amine ligands in these co-protected nanoclusters protected the nanoclusters with an identical coordination mode.Au18Ag18,Ag34Au8 and Ag5Au10 were built up with incomplete icosahedral Au11,icosahedral Au13 and tetrahedral Au4 building units respectively.By comparing the structure and optical properties of Ag34Au8 and Ag55Au6 clusters which both assembled from 4 icosahedral Au13 units but had a different assembled pattern,we could demonstrate that different patterns had certain significance to the optical properties of nanoclusters.In the end,we synthesized three ligands(amine,chloride and phosphine)co-protected coinage metal nanoclusters:[Au14Ag16(dpam)7(PPh3)6C14](SbF6)4 and[Ag31Au31(dpam)16(PPh3)Cl11](SbF6)5.Au14Ag16 cluster consisted of two icosahedral Au13 units.Owing to the presence of three ligands,Ag31Au31 cluster consisted of several cuboctahedra and icosahedral Au13 units.Then,we observed the amine ligands were parallel in the Ag53(dpam)18Cl6 nanocluster which were beneficial to the stability of the whole system.