Raman Spectroscopy of the Charge Transfer Complex (TTF)x C60 Br8

Abstract

We report Raman studies on powder samples of the charge transfer complex (TTF)(x)C60Br8 at room temperature. The phonons show considerable softening with respect to the frequencies observed in the Raman spectrum of solid C60Br8. The strongest mode at 1464 cm(-1) in C60Br8 is red shifted to a doublet with peaks at 1414 and 1421 cm(-1), implying an average phonon softening Delta omega of -47 cm(-1). A comparison with the phonon softening of the corresponding A(g)(2) mode in alkali-doped C-60 (Delta omega similar to -36 cm(-1) for A(6)C(60), A = K, Rb or Cs) suggests that 8 electrons are transferred per C60Br8 molecule in the charge transfer complex. The mode at 503 cm(-1) in C60Br8 is shifted upwards, similar to that in A(6)C(60) compounds