Closing the Shell: Gas-Phase Solvation of Halides by 1,3-Butadiene.

Gas-phase solvation of halides by 1,3-butadiene has been studied via a combination of photoelectron spectroscopy and density functional theory. Photoelectron spectra for X- ⋯(C4 H6 )n (X=Cl, Br, I where n=1-3, 1-3 and 1-7 respectively) are presented. For all complexes, the calculated structures indicate that butadiene is bound in a bidentate fashion through hydrogen-bonding, with the chloride complex showing the greatest degree of stabilisation of the internal C-C rotation of cis-butadiene. In both Cl- and Br- complexes, the first solvation shell is shown to be at least n = 4 ${n = 4}$ from the vertical detachment energies (VDEs), however for I- , increases in the VDE may suggest a metastable, partially filled, first solvation shell for n = 4 ${n = 4}$ and a complete shell at n = 6 ${n = 6}$ . These results have implications for gas-phase clustering in atmospheric and extraterrestrial environments.