We investigated powder absorption spectra of the donor BEDO-TTF and so
me radical salts of BEDO-TTF, which are metals even at low temperature
s. After an assignment of the bands in the neutral donor we found in t
he radical salts different vibrational frequencies of bands correlated
with C-O vibrations. These frequencies are directly related to the av
erage charge on the donor molecule. Additionally frequencies of CH2-st
retching vibrations exhibit differences, which can be ascribed to a va
rying strength of donor-anion interaction depending on the respective
anion.