Monolayer protected clusters: Synthesis, electrochemistry, ligand exchange kinetics and optical properties.

摘要

Chapter One is an introduction to fundamental properties of Monolayer-Protected Gold Clusters (Gold MPCs) including their synthesis, composition and structure, electrochemistry, ligand exchange mechanism and optical properties.; Chapter Two investigates medium effects (supporting electrolyte concentration, type and solvents) on the quantized double layer (QDL) charging capacitance of hexanethiolate coated gold cluster Au140(SC6) 53.; Chapter Three describes the effects of supporting electrolyte concentration, temperature and solvent environment on the capacitance of molecule-like phenylethanethiolate coated gold clusters Au38(SC2Ph)24 at +1 core charge state with square wave voltammetry (SWV), differential pulse voltammetry (DPV). The effects are interpreted with both the classical double layer theory treating the two continuous oxidation peaks as quantized double layer (QDL) charging peaks of a monolayer protected gold cluster (MPC) and the concept of "molecular capacitance" treating them as a succession of oxidization peaks of a molecule.; Chapter Four compares the kinetics of exchanges of phenylethanethiolate ligands (PhC2S-) on the monolayer-protected clusters (MPCs) Au38(SC2Ph) 24 and Au140(SC2Ph)53 with p-substituted arylthiols (p-X-PhSH), where X = NO2, Br, CH 3, OCH3, and OH at 293 K.; Chapter Five investigates a molecule-like substituent effect on redox formal potentials in the nanoparticle series Au38(SPhX) 24. Electron-withdrawing "X" substituents energetically favor reduction and disfavor oxidation, and give formal potentials that correlate with Hammett substituent constants. The ligand monolayer of the nanoparticles is shown thereby to play a strong role in determining electronic energies of the nanoparticle core, and is more than simply a protecting or capping layer. The substituent effect does not, however, detectably change the homo-lumo gap energy.; Chapter Six investigates the ligand dependent optical properties of Au38(SC2Ph)24 upon ligand exchange with different incoming thiols in THF. It was found that the luminescence of Au38(SC2Ph) 24 was enhanced more when more polar thiolate ligands were exchanged.; Chapter Seven describes the synthesis and characterization of ligand exchange product of Au55(PPh3)12Cl 6 with pentafluorobenzenethiol. The exchange product was characterized by electrochemistry, TGA, TEM, HPLC, UV-vis, Fluorescence, 1H and 19F NMR spectroscopy. (Abstract shortened by UMI.)