Exploring the gas-phase properties of coinage metal clusters and their interactions with small alkenes

The discovery of the size-dependent catalytic activity displayed by coinage metal clusters supported on metal-oxide substrates has led to the questions of what are the intrinsic properties of these clusters and how do they interact with catalytically relevant ligands. In order to address some of these issues, temperature-dependent equilibrium methods have been used to determine the sequential bond dissociation energies (BDEs) and association entropies for the attachment of C2H4 and C3H6 ligands to ground-state Agm+ (m < 14) clusters. Binding energies and association entropies were also measured for the sequential addition of C2H4 ligands to Agm- (m < 14) and to Aum+ (m = 1,3-9) clusters.; For the silver systems, where both the cations and anions were investigated, variations in metal-ligand BDEs are examined in detail both as a function of sequential ligand addition to a given Agm+/- cluster and as a function of Agm+/- cluster size for the first ligand additions. Additionally, changes in the metal cluster conformations driven by ligation energetics have also been observed for both the silver and gold clusters. For all systems studied, electronic structure calculations were performed using density functional theory (DFT) at the B3LYP level in order to determine the theoretical parameters important to the nature of the bonding of these clusters.; Irreversible reactions of ground-state Ag2+ with either ethene or propene led to both simple ligand addition and loss of neutral Ag to form ligated Ag+. Rate constants for the dissociation of Ag2+ via association of both ethene and propene have been measured. The measured rate constants exhibit a negative temperature dependence and relatively high reaction efficiency suggesting that the dissociation reactions are exothermic. Phase space theory (PST) and DFT were used to model the experimental rate data. Good agreement was found between experiment and theory for both systems.; Ion mobility methods have been used to determine collision cross-sections of Agm- (m = 3-12) clusters. The experimental collision cross-sections are compared to those of theoretical candidate structures whose geometries were calculated using DFT. These comparisons allow direct structural assignments to be made for the anionic silver clusters.