Synthesis Of Au₂₅（SR）₁₈ And Au₉₉（SPh）₄₂ Nanocluster And Study Of Gold Nanocatalysts For Sonogashira Reaction

Atomically precise gold particles have been emerged as a new functional material in the recent research, due to their unique size/shape-dependent optical and electronic properties that oppose to these of the gold atoms and bulk gold, and exhibit great applications in the novel catalysis, sensing, biology, and so on.Herein, we report the controlled synthesis of different size well-defined gold nanoparticles,further we researched the catalytic properties of gold nanoparticles in carbon-carbon coupling reaction and CO oxidation. The main work of this paper is as follows:1. We researched the controlled synthesis of the Au25(PPh3)io(SRi)5X2 nanorods (H-SR1:alkyl thiol, e.g., H-SC2H4Ph and H-S(n-C6Hi3)) and Au2s(SR2)18 nanospheres (H-SR2:aromatic thiol, e.g., H-SPh and H-SNap, H-SNap:2-naphthalenethiol) in the one-phase (in the CH2Cl2 solution) thiol etching reactions with excess thiols at room temperature. It is interesting that the aromatic thiol ligands perform conspicuous different with the alkyl ones in the etching reactions of the-1.3 nm polydisperse Aun(PPh3)m parent-nanoparticles, which are mainly attributed to their different electronic properties and the steric effects of the thiol ligands.Finally, the CeO2-supported Au2s(SC2H4Ph)18 and Au2s(SNap)18 nanosphere and Au25(PPh3)10(SC2H4Ph)sX2 nanorod catalysts exhibit different performance in the CO oxidation.2. We researched a new synthetic protocol of the Au99(SPh)42 nanoclusters with moderate efficiency (～15% yield based on the HAuCl4), via a combination of the ligand-exchange and "size-focusing" process. The purity of the as-prepared gold nanoclusters is characterized by matrix-assisted laser desorption ionization mass spectrometry and size exclusion chromatography.3. The catalytic activity of well-defined gold nanorods enclosed by Au(111) and Au(100) surfaces is investigated for the Sonogashira cross-coupling reaction between phenacetylene and 4-iodoanisole.This study shows that shorter nanorods(-33 nm) with more percentile of Au(111) surface are considerably more selective toward cross-coupling product (57% conversion with 90% selectivity forl-methoxy-4-(2-phenylethynyl)benzene (MeOPhC(?)CPh)). The selectivity of longer nanorods (e.g.,～42nm and ～50 nm) with more percentile of Au(100) surface as well as corresponding shapeless gold nanoparticles is found to be less than 59%. The catalytic mechanism of the homo-and cross-coupling reactions, in particular, roles played by Au(100) and Au(111) surfaces, is examined via DFT simulation. It is found that iodobenzene adsorption, C-I bond dissociation, reactants surface diffusions, and coupling reaction are more favorable to occur on Au(111) rather than Au(100). This work demonstrates the gold facet effect on catalytic coupling reactions, and the combined approach of experiment and theory permits mechanistic understanding at the molecular level.