Positional Order and Disorder of Symmetric and Unsymmetric BEDT-STF Salts

Abstract The symmetric ( s -) and unsymmetric ( us -) BEDT-STF (=bis(ethylenedithio)diselenadithia-fulvalene) salts were prepared, and their crystal structures and electrical resistivities were investigated. Four us -BEDT-STF salts have the positional disorder of the Se atoms in the STF framework in crystals, whereas three s -BEDT-STF salts have no disorder. When κ -( us -BEDT-STF) 2 GaCl 4 and κ -( cis-s -BEDT-STF) 2 GaCl 4 are compared, the latter without the positional disorder of the Se atoms is more conductive than the former one with the disorder.