Syntheses And Characterization Of Coin Metal Clusters Protected By Alkynyl And/or Phosphine

In the past few decades,great progress has been made in the synthesis,structural determination and performance studies of coinage metal nanoclusters.Monodisperse colloidal nanoclusters with well-defined molecular structure,which is very beneficial to investigate the correlation between their structure and properties,has caused great concern.Colloidal metal nanoclusters are mostly macromolecules composed of many components,so how to prepare and characterize nanoclusters is a huge challenge for scientists.It has been found that properties can be optimized by controlling the geometry and electronic structureds of the nanoclusters.A metal nanocluster usually consists of a metal core and peripheral ligands.The ligands are usually used as a stabilizer,and in many cases,they can affect the formation of nanoclusters,and even determine the size,shape and properties of the nanoclusters.Commonly used ligands include thiols,phosphines,halides,etc.In recent years,alkynyl ligands have been increasingly used for the synthesis of coinage metal nanoclusters due to their versatile coordination modes.In this paper,a series of silver and copper nanoclusters were synthesized using alkynyl and/or phosphine ligands.The main contents are divided into the following points:?1?The first all-alkynyl-protected [Ag₇₄?C?CPh?₄₄]?NO₃?₂ nanocluster was synthesized by using a bidentate phosphine ligand as an auxiliary ligand.The crystal structure was characterized by single-crystal X-ray diffraction.It was found that the core of Ag₇₄ is arranged in a Ag₄@Ag₂₂@Ag₄₈ three shell structure,and all phenylacetylenes coordinated with Ag in a ?3 mode.³¹P NMR results showed that dppp firstly combined with Ag atoms to form a dinuclear complex,and after the reduction,the Ag atoms were released to the phenylethynyl ligands.On this basis,the influence of the steric hindrance effect of the substituents at different positions on the cluster structure was also investigated,and two other [Ag₇₄?2-MePhC?C?₄₄]?NO₃?₂ and [Ag₇₄?3-Me Ph C?C?₄₄]?NO₃?₂ nanoclusters were synthesized.Mass spectrometry and single crystal analysis indicate that their cores are the same as Ag₇₄.Both are Ag₄@Ag₂₂@Ag₄₈ core-shell structures,each containing ?44? alkynyl ligands,and charge number of the skeletons are +2.In addition,an alkynyl-phosphine co-protected Ag₃₃?4-MePhC?C?22?dppp?4 nanocluster was synthesized,and its structure and optical properties are studied,the Ag atoms are arranged in a Ag₃@Ag₂₀@Ag₁₀ three shell structure.?2?We have successfully synthesized three alkynyl-phosphine co-protected Cu₅₃ nanoclusters containing Cu?0?,including Cu₅₃?C?CPhPh?₉?dppp?₆Cl₃?NO₃?₉,Cu₅₃?C?CPh?₉?dppp?₆Cl₃?NO₃?₉ and Cu₅₃?4-FPh C?C?₉?dppp?₆Cl₆-?OAc?₆,and the synthesis process,structure and properties were characterized in detail.X-ray single crystal analysis show that the 41 Cu atoms in the core of Cu₅₃ are layered in an unusual mixed FCC and HCP stacking sequence?ABABC?,while the bulk metallic copper usually featured FCC stack,giving strong evidence that Cu atoms can be arranged in non-FCC lattice at ambient condition when confined by proper ligands.To our knowledge,Cu₅₃ is also the copper nanoclusters with the most Cu?0?so far.And characterization methods including XPS,X-ray absorption,ESI-MS,IR and UV-visible spectroscopy etc.have been carried out.It is revealed that Cu^? first turned into Cu^? when coordinated with phosphine.The following addition of Na BH₄ and aging step further reduced it to Cu₅₃.The effects of different electron withdrawing groups on the structure and catalytic properties of the clusters were also investigated.?3?A top-down approach has been developed to synthesize three novel alkynyl and phosphine protected Cu???clusters whose structure and properties are well defined,including Cu₄dppp₃?PhC?C?₃]?NO₃?₂ with a rare centered triangular planar configuration,a trigonal prism type [Cu₆dppe₃?PhC?C?₅]NO₃,and a zigzag Cu₄dpph₂?PhC?C?4.Mechanism study indicated Cu nanoparticles were gradually oxidized at ambient condition to give CuO and Cu₂O as precipitate and Cu cluster was crystallized from the supernatant.In addition,the two planar Cu₄ clusters,especially Cu₄dppp₃?PhC?C?₃]?NO₃?₂,indicate outstanding luminescent properties,the quantum yield is as high as 69.84%.