Trifluoromethylsulfonyl-Based Salts of BEDT-TTF: Crystal and Electronic Structures and Physical Properties11

Abstract

Three 2 : 1 salts of the organic donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) with trifluoromethylsulfonyl-based anions N(SO 2CF 3) 2 −, CH(SO 2CF 3) 2 − and C(SO 2CF 3) 3 − were prepared by electrocrystallization. These salts were characterized by single-crystal X-ray diffraction, electron spin resonance (ESR) spectroscopy, electrical resistivity measurements and electronic band structure calculations. (ET) 2N(SO 2CF 3) 2 is a two-dimensional (2D) metal, but its ESR spin susceptibility above 150 K shows a weakly semiconducting behavior, presumably because during ESR measurements the sample cooling rate is slow hence allowing the disordered anions to readjust their positions. (ET) 2CH (SO 2CF 3) 2 is a 2D metal and undergoes a metal-to-insulator (MI) transition at 110 K due probably to a geometry change of the donor molecule layers. (ET) 2C(SO 2CF 3) 3 is a one-dimensional (1D) metal and undergoes an MI between 180 and 240 K, which is expected to be of charge density wave type.