Evidence of the Jahn-Teller splitting of C60- in C60-tetraphenylphosphoniumchloride from an electron-spin-relaxation study.

Abstract

Pulsed EPR measurements of the transverse and longitudinal relaxation times of the ${\mathrm{C}}_{60}^{\mathrm{\ensuremath{-}}}$-anion radical in crystalline ${\mathrm{C}}_{60}$-tetraphenylphosphoniumchloride were done at temperatures from 4 to 40 K. Above 40 K to room temperature the longitudinal relaxation time was taken from the cw-EPR linewidth. The low-temperature data are explained in terms of local magnetic fluctuations, slow ${\mathrm{C}}_{60}^{\mathrm{\ensuremath{-}}}$ motion, and localized two-level states related with the local disorder. The relaxation data at higher temperatures reveal experimental evidence for the Jahn-Teller distortion of the ${\mathrm{C}}_{60}^{\mathrm{\ensuremath{-}}}$-anion radical and allow to determine the Jahn-Teller splitting between the ${\mathit{a}}_{2\mathit{u}}$ electronic ground state and the excited ${\mathit{e}}_{1\mathit{u}}$ state of the unpaired electron.