Synthesis and X-ray crystal structures of radical cation salts of benzo-TTF derivatives with Cu2Cl62−, CuCl42− and ClO4− anions

► Synthesis and X-ray characterization of (CETBz-TTF)2[CuCl4] and paramagnetic Cu(II) complex anion (CETBz-TTF)2[Cu2Cl6(H2O)2]. ► Cu(II)(ClO4)2 or Cu(II)Cl2 ion were used to chemicaly oxidize cyanoethylthio- and cyanoethylseleno-benzo-TTF. ► Two donors radical form strong dimers with short sulfur-sulfur contacts.