Structures and energetics of V-n(C6H6)(m)(+) clusters: Evidence for a quintuple-decker sandwich

V-n(C6H6)(m)(+) cluster ions were produced by laser vaporization/ionization of a vanadium rod into a mixture of helium and benzene. The clusters with m = n + 1 show strongly enhanced intensities. Ion mobility measurements and collision-induced dissociation experiments were used to determine the structure of the different species. Density functional theory calculations using the B-LYP parametrization were performed to provide candidate structures and energetics of these clusters. Comparison of experimental and theoretical model cross sections indicated these clusters have sandwich structures with an alternation of vanadium atoms and benzene molecules. We also found that mass-selected V-n(+) clusters (n < 5) react with benzene, sequentially adding benzene neutrals to form terminal ions of formula V-n(C6H6)(n+1)(+). Mobility measurements on these ions strongly suggest they also have the sandwich structure, indicating major structural reorganization occurs when benzene interacts with the vanadium cluster.