Abstract
New bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-, bis(ethylenediseleno)tetrathiafulvalene (BEST)- and bis(ethylenedithio)tetraselenafulvalene (BETS)-based organic charge-transfer (CT) salts-alpha-(BEDT-TTF)(3)(HOC2H4SO3)(2)(1), beta-(BEST)(3)(HOC2H4SO3)(2)center dot H2O (2) and alpha-(BETS)(2)(HOC2H4SO3)center dot H2O (3)-have been prepared. Salts1and2show semiconducting behaviour. Salt3, which is almost isostructural to alpha-(BETS)(2)I-3, shows metallic behaviour down to 70 K and then shows a broader metal-insulator transition than that of alpha-(BETS)(2)I-3. 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.