Structures and Properties of New Organic Conductors: BEDT-TTF, BEST and BETS Salts of the HOC₂H₄SO₃⁻ Anion

Abstract

New bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-, bis(ethylenediseleno)tetrathiafulvalene (BEST)- and bis(ethylenedithio)tetraselenafulvalene (BETS)-based organic charge-transfer (CT) salts—α-(BEDT-TTF)3(HOC2H4SO3)2 (1), β-(BEST)3(HOC2H4SO3)2·H2O (2) and α-(BETS)2(HOC2H4SO3)·H2O (3)—have been prepared. Salts 1 and 2 show semiconducting behaviour. Salt 3, which is almost isostructural to α-(BETS)2I3, shows metallic behaviour down to 70 K and then shows a broader metal–insulator transition than that of α-(BETS)2I3. The reason for the difference in behaviour is estimated by the comparison of the Madelung energies of the full set of patterns of possible donor’s charge-ordered and anion’s disordered states.

Keywords

• organic conductors
• bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)
• bis(ethylenediseleno)tetrathiafulvalene (BEST)
• bis(ethylenedithio)tetraselenafulvalene (BETS)
• electrical resistivity
• magnetic susceptibility