Structural Regulation And Properties Of Zwitterionic Benzenethiolate-Protected Silver Nanoclusters

Silver thiolate nanoclusters have gradually become the focus of current research due to their diverse structures and their extensive applications in fluorescence,catalysis,biomarkers,and optical activity.Due to the large number of silver ions and ligands involved in the self-assembly process,the preparation of silver thiolate clusters with novel structures using efficient synthesis strategies still faces a great challenge.Previous results showed that the ligand exchange or anion template method can make the self-assembly process relatively controllable.But there is still a lack of mature theoretical and/or experimental guidance to achieve the accurate adjustment of the silver thiolate cluster structure and the functionalization of silver thiolate nanoclusters.In this thesis,solvent stimulation(dissolution-recrystallization)method was used to achieve reversible isomerization of silver/Tab(Tab=4-(trimethylammonio)benzenethiolate)clusters,while the anion templating method was used to synthesize silver thiolate clusters with intrinsically chiral kernel in a achiral environment.The structures and properties of the synthesized silver/Tab clusters were characterized by various methods including X-ray single crystal diffraction analysis,polycrystalline X-ray diffraction analysis(PXRD),and electrospray mass spectrometry.The pertinent results are briefly summarized as follows:1.Solvent-induced isomerization of silver/Tab clusters.We dissolved silver salts and zwitterionic Tab ligand in different solvent systems and obtain three silver/Tab cluster isomers Ag12(Tab)6(TFA)12(H2O)2·4CH3CN(1),Ag12(Tab)6(TFA)12·2DMF(2)and Ag12(Tab)6(TFA)12(CH3CN)2·2TFA(3).These Ag12 isomers with their silver skeletons in different symmetries can achieve the reversible structural transformation through the dissolution and recrystallization process.It was feasible to re-organize the silver/Tab clusters after dissolving them in a solvent with a stronger coordination ability,and the structural transformation happened.The isomerization process can be confirmed by PXRD,and the detailed crystal structure analysis also illustrated the mechanism of the structural transformation.This work not only serves as a new example of the isomerization of Ag(I)/Tab clusters,but also enriches the structural diversity of cluster-based frameworks with silver thiolate clusters as nodes2.Synthesis and characterization of chiral silver/Tab clusters controlled by anionic templates.By introducing an anionic template into the system,we synthesized three chiral Ag22 clusters with symmetry in the T-point group from the achiral environment:a silver/Tab cluster using bromide as a template---[Br@Ag22(Tab)12(TFA)4(DMSO)12]-(TFA)5(PF6)12(4);a silver/Tab cluster with iodide as a template---[I@Ag22(Tab)12(TFA)4-(DMSO)16](TFA)5(PF6)i2(5)and a silver/Tab cluster with sulfate as a template---[SO4@Ag22(Tab)12(TFA)4(DMSO)16](TFA)(PF6)15(6).The chiral silver/Tab clusters have a truncated tetrahedral silver skeleton and contain four twisted hexagons and triangles with shared edges.The entire structure of Ag22S12 is composed of a center-symmetric Agio polyhedron and a chiral Ag12S6 shell framework.Both the core and the shell are passed by four 3-fold axes through four apical silver triangles.And the middle point of the long edges of hexagonal faces are passed by three 2-fold axes.The chirality of Ag22 clusters is verified through the detailed analysis of their crystal structure.Such a homochiral crystallization was confirmed by the SCXRD analysis of single crystals randomly picked out from one batch.By using chloride as a template,a centrosymmetric silver/Tab cluster[Cl2@Ag22(Tab)14(TFA)6(DMSO)12](TFA)4(PF6)10·8DMSO(7)was obtained from the analogous reaction.The above results demonstrated that the size of the anion can affect the self-assembly process of the silver/Tab clusters in solution greatly.This work not only proposes a strategy for the direct synthesis of chiral silver/Tab clusters in an achiral environment,but also extends the application of the anionic template method in the preparation of novel silver thiolate nanoclusters.