Structural and physical properties of new conducting cation radical salts with Te-based counteranions, tetraiodotellurate(II) and hexaiododitellurate(II)

This article reports preparation, structure, and conducting property of several cation radical salts of organic donors tetramethyltetrathiafulvalene (TMTTF), ethylenedithiotetrathiafulvalene (EDT-TTF), bis(ethylenedithio)tetrathiafulvalene (ET), bis(ethylenedithio)tetraselenafulvalene (BETS) and hexamethylenetetraselenafulvalene (HMTSF) with two novel planar Te-based dianions, TeI42- and Te2I62-. (ET)(5)Te2I6 1 and 4 6 12(BETS)(5)Te(2)I6 2 are isostructural. In these Te-2 I-6(2-) salts, intermolecular short (I) (. .). I contacts form a supramolecular corrugated anion sheet. Donor arrangement is similar to the theta-type. With lowering temperature, the resistivity of 1 shows a gradual increase followed by a sharp upturn at 110K. 2 is metallic down to 120K and shows a gradual increase of the resistivity followed by a clear transition to an insulating state around 60K. Crystal structure of (ET)(4)TeI4 3 is based on the "herring bone" arrangement of ET molecules similar to the octype. 3 shows a semiconductive behavior around room temperature followed by a transition to an insulating state at 210K. (EDT-TTF)(4)TeI4 4, a semiconductor, exhibits a unique two-dimensional arrangement of dimerized EDT-TTF molecules. (C) 2002 Elsevier Science (USA).