Structures and Properties of New Organic Molecule-Based Metals, (D)₂BrC₂H₄SO₃ [D = BEDT-TTF and BETS]

An organic anion, 2-bromoethanesulfonate (BrC2H4SO3-), provides one bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and two bis(ethylenedithio)tetraselenafulvalene (BETS) salts, the compositions of which are beta''-beta''-(BEDT-TTF)(2)BrC2H4SO3 (1), beta''-beta''-(BETS)(2)BrC2H4SO3 (2), and theta-(BETS)(2)BrC2H4SO3 (3), respectively. Compound 1 shows a metal-insulator transition at around 70 K. Compound 2 is isomorphous to 1, and 3 is polymorphic with 2. Compounds 2 and 3 show metallic behavior at least down to 4.2 K. The pressure dependence of the electrical resistivity of 1 is also reported.