C60 fullerene and its molecular complexes under axial and shear deformation

Abstract

We have studied the pristine C60 and its molecular complexes with the organicdonors bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF or ET) andtetramethyltetraselenafulvalene (TMTSF) by means of ESR and Ramanspectroscopy at high pressure. The important changes in the ESR signal of C60were observed under axial pressure combined with shear deformation. It is shownthat the treatment at a anisotropic pressure of 4 GPa results in a reduction in thesymmetry of the C60 molecule and the formation of radicals. Treatment of themolecular complex of (ET)2·C60 at a pressure of ∼4.5 GPa and a temperature of150°C leads to the formation of C60 dimers. The Raman spectra of themolecular complex C60·TMTSF·2(CS2) were measured in situ at ambienttemperature and pressures up to 9.5 GPa. The pressure behaviour of the Ramanpeaks reveals singularity at 5.0 ± 0.5 GPa related to the softening andsplitting of some of the phonon modes. The residual softening of the Ag (2)mode is the same as in the case of KC60, which may be an indication that thetransition has a charge-transfer character, resulting in the formation of theC60−1anionic state charge-transfer complex.