Dynamics of Carbonium Ions Solvated by Molecular Hydrogen: CH5+(H2)n (n = 1, 2, 3).

The dynamics of the carbonium ion (CH(5)(+)), a highly reactive intermediate with no equilibrium structure, was studied by measuring the infrared spectra for internally cold CH(5)(+)(H(2))n(n = 1, 2, 3) stored in an ion trap. First-principle molecular dynamics methods were used to directly simulate the internal motion for these ionic complexes. The combined experimental and theoretical efforts substantiated the anticipated scrambling motion in the CH(5)(+) core and revealed the effect of the solvent molecular hydrogen in slowing down the scrambling. The results indicate the feasibility of using solvent molecules to stabilize the floppy CH(5)(+) ion in order to make it amenable to spectroscopic study.