Raman spectroscopy of BEDT-TTF trihalide salts containing BrxIyCl1−x−y anions

We demonstrate the ability of Raman spectroscopy to detect and identify trihalide anions in BEDT-TTF salts. In case of Br x I y Cl 3-x-y trihalide anions the vibrational spectroscopy allows a qualitative determination of anion compositions. Polarised Raman spectra as well as energy dispersive microanalysis provide evidences that β-(BEDT-TTF) 2 Br x I y Cl 3-x-y , β-(BEDT-TTF) 2 Br x I y Cl 3-x-y and β-(BEDT-TTF) 2 I x Cl 3-x contain mixtures of the (I-I-I) - , (Br-I-I) - , (Br-I-Br) - , (Br-I-Cl) - , (I-I-Cl) - and (Cl-I-Cl) - anions. Some of the observed Raman bands are assigned to the Σ + modes of the linear non-symmetrical (Br-I-I) - , (I-I-Cl) - , (Br-I-Cl) - anions, while others are recognised as the Σ g + modes of symmetrical (I-I-I) - , (Br-I-Br) - or (Cl-I-Cl) - anions.