Raman study of the charge transfer C 60 complexes with tetraphenylphosphonium halides

Abstract

Raman spectra are presented for single crystal charge-transfer complexes of fullerene and tetraphenylphosphonium halides, (Ph 4P) 2C 60Y (Y = Cl, Br, I). The Raman spectrum is found to be insensitive to the halogen ion indicating the intrinsic character of this spectrum. The spectra of complexes excited at 514.5 nm look very different from those excited at 647.1 nm; especially the low-frequency modes are stronger in the Raman spectrum excited at 647.1 nm. The 1469 cm −1 pentagonal pinch mode of C 60 is shifted and split in these complexes, a double-peak structure with components at 1462 and 1452 cm −1 is observed. All these results are understood as due to the presence of C − 60 in crystalline sites of low symmetry.