| Coinage metal nanoclusters are one of the hot topics in nanoscience,which are unique in atomic precision,monodispersity and attractive properties.In scientific research,revealing the precise structure of metal nanoclusters is of great significance,because the well-defined structure is fundamental to understanding the surface(including composition,organic-metal interface,arrangement of ligands),structure-property relationships and growth mechanisms.At present,silver nanoclusters are less researched than gold nanoclusters due to their susceptibility to oxidation and poor stability.Therefore,it is crucial to develop new synthetic strategies to deepen the understanding of assembly process and precisely control of core size.In this thesis,we constructed a series of novel silver nanocluste rs based on the macrocyclic thiacalix[4]arene ligands under the guidance of anion templates.The solution behavior,assembly mechanism,and transformation process were investigated in detail by ESI-MS.The main research work of this thesis is as follows:I The silver nanoclusters protected by thiacalix[4]arene-based metalloligandWith a stepwise assembly strategy,hexagonal and rectangular Ag18 nanoclusters were constructed using Mo2O5(PTC4A)2]6-(H4PTC4A:p-phenyl-thiacalix[4]arene)as metalloligand in non-alcohol and alcohol solvents,respectively.The molecular formulas are determined by single crystal X-ray diffraction(SCXRD)to be[Ag18(Mo2O5PTC4A)6(EtS)6(Tos)2]2Ag(CH3CN)3 4CHCl3(1)and Ag18S{Mo2O5(PTC4A)2[MoO2(nprO)][(MoO(nprO)2]}2(CyS)6(Tos)2(nPrO)2(2).ESI-MS plays a crucial role in the study of the assembly mechanism:(i)Identifying[Mo2O5(PTC4A)2]6-metalloligand in the first step to guide the synthesis;(ii)Detecting intermediates in the reaction process to explain the different configurations of Ag18 nanoclusters.Combined with ESI-MS and SCXRD analysis,it is shown that the metalloligand can be cyclized to form[(Mo2O5PTC4A)6]12-metallamacrocycle in non-alcohol solvents,and then construct hexagonal Ag18 nanocluster;Or deprotonated n-propanol coordinates MoⅥ to terminate such condensation,resulting in rectangular Ag18 nanocluster.The universality of this solvent-controlled metalloligand condensation strategy is further demonstrated by a series of related crystallographic data(3-13).In addition,the corresponding metalloligand species(14-15)were successfully crystallized and structurally characterized.The design and application of[Mo2O5(PTC4A)2]6-metalloligand in this work not only provide a feasible route for the rational assembly of silver nanoclusters,but also bring a new idea for the controllable ligand metallization and subsequent condensation.Ⅱ Temperature-controlled selective synthesis of silver nanclusters and structural transformationTwo atomically accurate silver nanoclusters were synthesized from p-tert-butylthiacalix[4]arene(H4TC4A),[CySAg]n,AgOAc,K2Cr2O7 at 20 and 80℃,respectively.The molecular formulas are[(CrO4)6@Ag54Cl(TC4A)6(CyS)15(OAc)2(CH3CN)2]·3CH3CN(16)and[(CrO4)Cl3@Ag33(TC4A)4(CyS)10(OAc)2(CH3CN)2]·4CH3CN·2CH2Cl2(17).ESI-MS analysis showed that the stability of compound 17 was better than that of compound 16.Furthermore,the difference in structural stability inspired us to explore 1,4-dipyridylbenzene(bpbenz)stimulation-induced transformation starting with compounds 16 or 17.We found that the former can form an Ag3i dimer,{[(CrO4)Cl3@Ag31(TC4A)4(CyS)10(bpbenz)1.5]·5CH3CN·CH2Cl2}2(18),undergoing a vigorous dissociation-recombination process,while the latter can also obtain the same product through a non-destructive ligand exchange process.Time-tracking ESI-MS gives detailed transformation path in solution.This work not only demonstrates how synthesis temperature controls the separation of specific phases,but also reveals the structural transformation pathways of nanoclusters with different stability.Ⅲ Synthesis and characterization of a high-nuclearity silver nanocluster encapsulating classical[V10O28]6-anionA polyoxovanadate(POV)-based 50-nuclei silver nanocluster,[V10O28@Ag50(tBuPhS)32(CF3COO)8(DMF)6(H2O)4]·2DMF·4CF3COO(19),was successfully synthesized using anion template strategy with the participation of H4TC4A ligand.Here,the largest known POV-templated silver nanocluster has been synthesized and fully characterized.X-ray single crystal diffraction confirmed that the structure is a typical core-shell structure,which consists of in-situ generated classical[V10O28]6-core and Ag50 shell.The surface of the silver nanocluster is protected by tBuPhS-,CF3COO-,DMF and H2O ligands.The box-shaped{V10O28@Ag50} realizes the geometric inheritance from decavanadate with D2h symmetry to the silver skeleton.Interestingly,ESI-MS detected a series of Ag46～Ag50 species accompanied by ligand exchange,giving us a comprehensive understanding of their abundant dynamic behavior in solution.The PXRD and IR spectra confirmed the great stability of the cluster in solid state.This work sheds light on the further construction of POV-templated high-nuclearity silver clusters. |
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