Luminescence spectroscopy of C70 and C70Ph2 in crystalline toluene at 5 K

Luminescence spectra for fullerene [70] with two phenyl groups covalently attached (C70Ph2) was recorded at room temperature and at low temperature in a crystalline toluene matrix. Finely resolved luminescence spectra (Shpolʹskii effect) are observed at 5 K under excitation at 514 nm. We assign an intense line at 780.2 nm as the origin band of the S1–S0 transition. By comparison with the fluorescence spectrum of C70 in toluene at 5 K, two other bands located at shorter wavelength are tentatively identified as the origin lines of the S2–S0 and S3–S0 transitions. It results from these assignments that the effect of adding two phenyl groups to the fullerene cage produces a 116.3 nm red-shift of the fluorescence of C70Ph2 as compared with the fluorescence in C70.