CATION-AROMATIC PI-INTERACTION IN THE GAS-PHASE - AN EXPERIMENTAL-STUDY ON RELATIVE SILVER (I) ION AFFINITIES OF POLYAROMATIC HYDROCARBONS

Abundant silver (I) ion bound asymmetric dimers of polyaromatic hydroc arbons (PAHs) were easily generated by electrospray ionization, Based on the unimolecular decomposition of the Ag(I) ion bound asymmetric di mers, the relative Ag(I) ion affinities of nine PAHs in the gas phase has been established as: benzene < naphthalene < phenanthrene < anthra cene < fluoranthene < pyrene < triphenylene < chrysene < benz[a]anthra cene. The observed Ag(I) ion affinities were found to correlate with c alculated quadrupole moments of PAHs, indicating that electrostatic ch arge-quadrupole interaction is important in the cation-aromatic pi bin ding of the polyaromatic systems being studied, However, secondary eff ects, such as surface area of the aromatic pi electrons or intermolecu lar electronic repulsion and steric repulsion between bay region hydro gens, could also affect the magnitude and relative order of Ag(I) ion affinities of PAHs, (C) 1998 John Wiley & Sons, Ltd.