RAMAN-STUDY OF THE CHARGE-TRANSFER C-60 COMPLEXES WITH TETRAPHENYLPHOSPHONIUM HALIDES

Raman spectra are presented for single crystal charge-transfer complex es of fullerene and tetraphenylphosphonium halides, (Ph4P)(2)C60Y (Y = Cl, Br, I). The Raman spectrum is found to be insensitive to the halo gen ion indicating the intrinsic character of this spectrum. The spect ra of complexes excited at 514.5 nm look very different from those exc ited at 647.1 nm; especially the low-frequency modes are stronger in t he Raman spectrum excited at 647.1 nm. The 1469 cm(-1) pentagonal pinc h 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 the se results are understood as due to the presence of C-60(-) in crystal line sites of low symmetry. (C) 1997 Elsevier Science B.V.