Structure And Properties Of Aromatic Mercaptans Protected Silver Nanoclusters

Metal nanoclusters have size-dependent electrical,magnetic,optical and other properties,and have potential applications in the fields of catalysis,sensing,medicine,and solar cells.How to realize the controllable preparation of metal nano-clusters is of great significance for the further design and application of multi-functional nano-clusters.Therefore,we have carried out in-depth research work on ligand-protected silver nanoclusters.Different ligand assembly strategies were used to control the structure and composition of nanoclusters at the atomic level,and a series of univalent and mixed-valent silver nanoclusters protected by aromatic mercaptan ligands were obtained.The main contents are as follows:1.Mercaptan ligands（such as 2,4-dimethylthiophenol,4-aminophenol and cyclohexanethiol）with different structural characteristics were selected.Five Ag（I）nanoclusters with different nuclear numbers were obtained by phosphine ligand regulation:Ag₁₄S（SC₆H₃Me₂）₁₂（TPP）₆（1）,Ag₁₄S（SC₆H₃Me₂）₁₂（DPPy）₆·（DCM）（2）,Ag₈Cl₄(C₆H₁₂S)₂（DPPF）₄·（SbF₆）₂（3）,Ag₃₇S₂(C₆H₁₂S)₃₀（TPP）₅·（SbF₆）₃（4）and Ag₆（C₆H₇NS）₅（Dppb）₃·NO₃（5）.1 and 2 have the same framework which contain a rare structures which set of distorted cube[Ag₈S]⁶⁺capped by AgS₂P secondary structure.3 is a distorted polyhedral Ag₈Cl₄S₂P₈,while 4 has a multi-layer sandwich structure with a high-nuclearity cluster structure.The core of the structure is a distorted pentagonal Ag₅S_5.Intermediate layer is a double pentagonal Ag₁₀S₁₂.The outermost layer is a fake-double pentagon ring Ag₂₅S₁₅.5 is an example of a six-core silver cluster with an open skeleton,in which the C₆H₇NS ligand with two coordination modes（μ₂ andμ₃）bridges six silver atoms.In addition,UV-vis show that both 1 and 2 have good stability.2.Using three mercaptan ligands（4-isopropylphenol,3,4-dichlorophenyl thiophenol,cyclohexanethiol）and one aromatic alkynyl ligand（4-fluorophenylacetylene）as the main ligand.Six cases of mixed valence silver nanoclusters with different number of cores were obtained from the type of auxiliary ligand（halogen,phosphine）.For example,using 4-isopropyl thiophenol as the main ligand,three silver nanoclusters with different sizes were obtained by regulating the type of halogen.[Ag₆₄S₃₂（SCH₂C₆H₄^t Bu）₂₈&Ag₆₆S₃₂（SCH₂C₆H₄^t Bu）₂₉]（PPh₄）_x（6）was protected by pure thiol ligand.While[Ag₁₃₄Br₂（SCH₂C₆H₄^tBu）₇₅]（PPh₄）₂（7）and Ag₁₁₈Cl₂（SCH₂C₆H₄^t Bu）₈₁（8）were protected by thiol and halogen atoms.To be noted,6 is a rare high-nuclearity mixed-valent silver cluster protected by pure mercaptan ligands.There are co-crystallized Ag₆₄4 cluster and Ag₆₆6 cluster.The core of both clusters is Ag₁₇7 with ABA accumulation,but the peripheral belt part is different from a Ag₂S unit.Surprisingly,with adding bromide ions into the solution of 6,6 can be converted to nuclear and larger 7.The core unit of 7 is Ag₅₁(Ag₇@Ag₃₂@Ag₁₂),the surface"belt"is Ag₅₅S₇₅5 and the top-and-bottom"hat"is Ag₃₀Br₂.The composition of 8 is:Ag₁₉@Ag₅₀@Ag₄₉.The core of the cluster Ag₁₉is a double-capped pentagonal prism interspersed with two pentagonal bipyramid Ag₁₃.The second layer is the"rugby"Ag₅₀,and the outermost"belt"is Ag₄₉.6 and 7 are two nano-clusters with high yield and good stability,and all of them have photocatalytic activity,which can degrade organic dyes under ultraviolet light irradiation.Additionally,6and 7 have excellent fluorescence quenching properties.The aromatic mercaptan ligand was replaced with cyclohexanethiol and an example of Ag₁₆₀Cl₂(C₆H₁₂S)₆₃（9）protected by mercaptan and chlorine was obtained.The whole structure is a closed cage structure composed of core Ag₅₅5 and surface layer Ag-SR/Cl.The core Ag₅₅5 is a cage structure composed of Ag₁₃@Ag₄₂2 nested.A kind of FCC silver cluster Ag₆₃（SC₆H₄Cl₂）₃₆（PPh₃）₈（10）was obtained with 3,4-dichlorothiophenol and monodentate phosphine.Its structure can be seen as a cube composed of Ag₁₃@Ag₃₀@Ag₁₂S₃₆@Ag₈.In addition,[Ag₁₉（dppm）₃（4-FPhC≡C）₁₄]（SbF₆）₃（11）was protected by both aromatic alkyne and phosphine ligand.Single crystal structural analysis revealed that Ag₁₉9 has D_3hh symmetry.