Synthesis And Properties Of Mo-POM Templated Sliver-Copper/Sliver Nanoclusters

Metal nanoclusters are crystalline materials formed by multiple metal ions gathered together and protected by peripheral organic ligands.Their diverse structures and rich physical and chemical properties have made them the focus of current research in chemistry and materials for a wide range of applications in fields such as luminescence,catalysis,chemical sensing,and electrochemistry.Metal nanoclusters,typically smaller than 3 nm in size,have precise chemical composition and structure and are an important bridge between small molecules and nanoparticles.As an important member of the coinmetal family,silver clusters have a rich structural conformation and promising applications.It is of great significance to study the precise structure of silver cluster-based materials,understand their complex assembly mechanism and structure-activity relationship,develop controllable and universal synthesis methods for silver clusters,and carry out related property research.In this thesis,we combine strategies such as heterometallated cores,increased volume of anionic templates,thermodynamically regulated peripheral ligands,and structural transformation reaction patterns under the guidance of anion-templated to rationally design and controlled synthesis novel silver cluster-based materials and further investigation of their catalytic and luminescent properties.The main research contents are as follows:1.The application of a silver acetylene precursor to the classical click chemistry key intermediate synthesis in the inversion reaction led to the successful isolation of a highly nucleated multishell Ag(I)-Cu(I)-POM alloy nanocluster:[(Mo4O16)2@Cu12@Ag54(PhC≡C)50](Ag54Cu12)in the presence of an anionic template.Two unconnected[Mo4O16]8-anions twisted about 24° from each other were encapsulated by the subshell Cu12 and shell Ag54 cages to form the final three-shell(Mo4O16)2@Cu12@Ag54 nanoclusters.The solid-state UV-Vis absorption spectrum of Ag54Cu12 indicates that it is a narrow bandgap semiconductor and exhibits a good photocurrent response.DFT calculations also indicate good optoelectronic properties of Ag54Cu12.In addition,Ag54Cu12 and Ag54Cu12/C were applied as catalysts in 1,3-dipole cycloaddition reactions,respectively,and showed good catalytic properties,demonstrating that Ag54Cu12 can be used as a heterometallic catalyst for the CuAAC reaction.This work represents a breakthrough in the synthesis of monovalent silver-copper alloy nanoclusters and realises the possibility of catalytic reactions with this type of alloy nanoclusters,providing an experimental basis for exploring the conformational relationships of such materials.2.In order to extend the reactions attributed to silver thiol precursors to obtain breakthrough results,we introduced a combination of divalent copper salt and copper powder into the cyclohexanethiol system to synthesise an example of a[Cu3(Mo4O16)2]10anionic template for silver clusters:[(Cu3(Mo4O16)2@Ag55(CyhS)43(CH3OH)(COOCF3)]·3H2O(Ag55).This new D3h-symmetric POM anion is formed by inserting three Cu ions between two cubic alkane homopolymolybdic acid[Mo4O16]8-,a polyanion encapsulated in an Agss cluster.prosilver interactions between the Ag ions and the outer end ligands via Ag-O and Ag-S interactions to stabilize the Agss shell.Solid state UV-vis absorption spectroscopy and photocurrent tests show that Agss is a wide band gap semiconductor with a good photocurrent response.This heterometallic POM anion template was encapsulated firstly in a silver cluster structure,and this work provides a new avenue for the construction of heterometallic anion templates guided synthesis of high-nuclearity Ag nanoclusters.3.Not only can individual anionic templates influence the size and shape of clusters,but the combination of multiple polyacid templates can be an important guide for the synthesis of highly nucleated and highly symmetric silver cluster structures.Using a mixed ligand protection and anion templating strategy,we have isolated an example of four[MoO4]2-anion templated,iPrC6H4S-and 1,3-bis(diphenylphosphine)propane(dppp)co-protected cationic silver clusters:[Ag13(MoO4)4(SC6H4iPr)2(dppp)8]3+(Ag13).The two capped Ag4SC6H4iPr units are connected to the intermediate Ag@Ag4 layer via four[MoO4]2-anion templates to form a three-layer D4h symmetric structure.The PL properties of orange-yellow-light Ag13 should be assigned to the ligand-to-metal-charge-transfer by DFT calculations.This work shows that the simple[MoO4]2-molybdenum POM anion also has potential to induce new structures,providing an idea for research progress in the synthesis of silver clusters with high symmetry.4.Through a mixing strategy,guided by multiple multi-acid templates we also obtained an example of the longest size chain-like highly nucleated silver cluster:[(MoO4)8@Ag90(CyhS)44(PhCOO)28]·2PhCOO(Ag90),with a microstructure size of 4.9×2.78 nm.the long chain structure of Ag90 is the result of eight[MoO4]2-anions separated by Mo-O,Ag-O interactions link the 90 silver atoms and the silver shell is protected by a combination of cyclohexanethiol and benzoic acid at the periphery.The red-emitting lowtemperature luminescent properties of Ag90 are caused by a charge transfer(LMCT)leap from the ligand S 3p to the metal Ag 5s orbital.This work provides a guiding strategy for the synthesis of ultra-high nuclei chain-like silver nanoclusters using simple anion-templated and represents a new development in the protection of silver clusters by carboxylic acid ligands.5.Crystal structure transformation and evolution is an important means of obtaining new cluster structures.In this chapter we isolate and characterize a pair of POM templated silver clusters,[(Mo7O24)@Ag46(CyhS)28(CF3COO)10(CH3CN)4]·2COOCF3 and[(Mo8O28)@Ag48(CyhS)24(CF3COO)16(CH3CN)4](Ag46 and Ag48),that can coexist in the same solution system.Both compounds are typical core-shell structures,with anion templates[Mo7O24]6-and[Mo8O28]8-as cores of the overall structure,templating the outer Ag-S shell to form a cluster structure with high nuclei.The composition of these two compounds was studied by characterization methods such as IR,EDS-Mapping,ESI-MS-TOF and XPS,and solid UV-Vis proved that Ag46 and Ag48 are potential wide-bandgap semiconductor materials with good photocurrent response.In terms of synthesis methodology,the existence of Ag46 and Ag48 species in different solution systems was studied by the "one-pot method",step-bystep synthesis and two-phase mutual conversion,and the conversion process from Mo7O24@Ag46 to Mo8O28@Ag48 was monitored by liquid ultraviolet.The development of this coexisting phase capture facilitates the study of phase diagram problems involving POMs templated silver nanoclusters in basic chemistry.