Gas-phase studies of group-11 cation (Cu+, Ag+, and Au+) reactions with 2-propanol in a supersonic beam-expansion source

The gas-phase reactions of group-11 ions (Cu+,Ag+, and Au+) with 2-propanol were investigated using laser vaporization combined with supersonic beam e xpansion in a time-of-flight mass spectrometer. A number of reaction pathwa ys, including assoication, dehydrogenation, and dehydration, were observed. Among these metal ions, Aut is highly reactive toward 2-propanol. The expe rimental results are parallel to studies by Wilkins ct al. using an FT-ICR mass spectrometer (J. Am. Chem. Sec., 107, 7316 (1985)). The geometries and binding energies of all complexes M+-L, where M+ = Cu+, Ag+,and Au+, L = 2 -propanol, acetone, propene, and H2O, were estimated using Moller-Plesset p erturbation (MP2) and density functional theory (BLYP). The bond strengths of the complex ions involving gold revealed the strongest bonding, due to a relativistic effect. The energetic relationship between the reactants and the products facilitated an interpretation of the observed exit channels. B ecause of the supersonic beam source employed, larger clusters containing m etal ions were generated as well. Because the cluster sizes with solvent mo lecules were greater than or equal to 2, the reactivities were apparently l imited to Cu+ and Ag+ clusters, while the reactive nature changed in Au+ al ong with the formation of acetone, lacking in the bare Au+ reactions. For l arger clusters, calculations on Ag+-(2-propanol)(2) and Ag+-(2-propanol)(ac etone) complexes using BLYP were performed to obtain their energetics.