High pressure optical properties of fullerene and fullerene derivatives

High-pressure Raman spectroscopy is a useful tool to investigate various pr essure-induced effects on fullerene and its chemical derivatives. In the ca se of pristine C-60 the pressure-induced freezing of molecular rotations ca uses the softening, while the lowering of symmetry causes the splitting of several phonon modes. In the neutral state donor-acceptor molecular complex C-60*TMTSF*2(CS2) high pressure leads to an irreversible charge-transfer p hase transition, associated with the transfer of one electron from TMTSF do nor to C-60 acceptor molecule. In the case of azafullerene (C59N)(2), the p ressure dependencies of the phonon frequencies exhibit reversible changes i n their slopes, associated with the attainment of the ideal HCP structure ( originally c/a = 1.623), as well as with the starting of the intradimer bri dge shortening. (C) 1999 Elsevier Science B.V. All rights reserved.