Mixtures of trihalide anions in isostructural BEDT-TTF salts as seen by Raman spectroscopy

Low frequency Raman spectra have been recorded at room temperature for P-type structure of the (BEDT-TTF)(2)X single crystals (where BEDT-TTF is bis(ethylenedithio) tetrathiafulvalene and X stands for mono or mixed trihalide anions). This technique has permitted us to detect a presence of the (Br-I-CI)(-), (I-I-Cl)(-) and (Cl-I-Cl)(-) anions in addition to a mixture of the (I-I-I)(-), (I-I-Br)(-) and (Br-I-Br)(-) anions in some recently grown single crystals. The observed low-frequency Raman bands were compared with the ab initio calculated vibrational frequencies of trihalide anions and a very good agreement between experimental and calculated data was found.