Aromatic−Rare Gas Complexes:  The Microwave Spectrum and Structure of the Fluorobenzene−Neon Dimer

The rotational spectrum of the fluorobenzene−neon complex was assigned. The structure of the complex was deduced from the rotational constants of the C 6 H 5 F− 20 Ne, C 6 H 5 F− 22 Ne, and C 6 D 5 F− 20 Ne species. The dimer has C s symmetry. The neon atom sits nearly above the center of the fluorobenzene at a perpendicular distance of 3.422(1) Å. It is shifted 0.13(1) Å from the center of the ring toward the fluorinated carbon atom. The structure is compared with a number of related aromatic−rare gas complexes (rare gas = Ne or Ar). Trends are discussed in view of dispersion, polarization, and repulsive forces.