Effects of Ion Pairing on the EPR Spectrum of the Naphthalene Anion in Solution

Data are presented for the proton and cation hyperfine coupling constants and $g$ values of the naphthalene anion as a function of solvent, cation, and temperature. The variation of the proton coupling with solvent and cation is comparatively small and somewhat irregular. The temperature coefficient of the proton coupling constants depends upon the cation. Cation coupling constants are reported for the five alkali ions, as well as the temperature dependence in some cases. The $g$ value of ion pairs containing Rb or Cs differ considerably from that of the free anion, and is temperature dependent. These observations are discussed qualitatively in terms of the formation and structure of ion pairs, and of the effects of the electrostatic field and spin–orbit coupling of the cation.