ET based conductors with different behavior of resistivity along and across conducting layers

摘要

A series of novel bis(ethy!enedithio)tetrathiafulvalene (ET) based radical cation salts with tetrahedral [HgBr_4]2- and [CdBr_4]~(2-) dianions of (ET)_4MBr_4(solvent) stoichiometry (M = Hg, Cd; solvent = C_6H_5X or 1,2-C_6H_4X_2, X = Cl, Br) has been prepared. Crystal structures of theta-(ET)_4HgBr_4(1 ,2-C_6H_4X_2) (X- Cl, Br) were found to involve conducting ET radical cation layers of the 9-type packing and insulating layers consisting of [HgBr_4]~(2-) anions and solvent molecules. The donor stacking directions of the neighboring conducting layers are perpendicular to each other. Depending on salt composition, intralayer electrical resistivity of theta-(ET)_4MBr_4(soIvent) showed metallike behavior down to temperatures varying within 4.3-100 K range. Electrical resistivity perpendicular to the layers revealed nonmetallic behavior