Semiconducting charge-transfer salts of BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene] with hexachlorometallate(IV) anions

Abstract

Two new crystalline charge-transfer salts of BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene] containing hexachlorometallate anions of 5d elements have been synthesised, characterised structurally and their magnetic and conducting behaviour investigated. α-(BEDT-TTF)₄ [ReCl₆ ]C₆H₅CN is triclinic [P1̄; a=9.455(2), b=11.306(3), c=18.193(5) Å; α=101.85(2), β=92.74(2), γ=110.52(2)°; Z=1]. Its structure consists of alternate layers of BEDT-TTF and of [ReCl6 ]2- C6H5CN, the former consisting of two crystallographically independent stacks, in one of which the molecules carry a charge close to +1 while in the other they are approximately neutral. The cations lie between the [ReCl6 ]2- moieties while the neutral molecules are closest to the C6H5CN species showing that the structure is determined by electrostatic interactions. (BEDT-TTF)2 [IrCl6 ] is likewise triclinic [P1̄; a=8.721(1), b=10.257(2), c=11.086(2) Å; α=111.00(1), β=98.31(1), γ=103.32(1)°; Z=1]. Its packing motif is new among BEDT-TTF salts, containing no discrete layers of anions and cations. Face-to-face BEDT-TTF dimers form an infinite three-dimensional network. Both compounds are semiconducting and their magnetic properties are dominated by the Curie–Weiss behaviour of the anions.

References

1. A. A. Galimzyanov, A. A. Ignatev, N. D. Kushch, V. N. Laukhin, M. K. Makova, V. A. Merzhanov, L. P. Rozenberg, R. P. Shibaeva and E. B. Yagubskii, Synth. Met., 1989, 33, 81.
2. V. E. Korotkov, V. N. Molchanov and R. P. Shibaeva, Sov. Phys. Crystallogr., 1993, 37, 776.
3. M. Z. Aldoshina, L. S. Veretennikova, R. N. Lubovskaya and M. L. Khidekel, Transition Met. Chem., 1980, 5, 63.
4. L. Ducasse, A. Abderrabba, J. Hoaran, M. Pesquier, B. Gallois and J. Gaultier, J. Phys. C: Solid State Phys., 1986, 19, 3805; L. Ducasse and A. Fritsch, Solid State Commun., 1994, 91, 201.
5. K. Bender, I. Hennig, D. Schweitzer, K. Dietz, H. Endres and H. J. Keller, Mol. Cryst. Liq. Cryst., 1984, 108, 359.
6. P. Guionneau, C. J. Kepert, D. Chasseau, M. R. Truter and P. Day, Synth. Met., in press.
7. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, Wiley, New York, 1988, 5th edn.
8. E. M. Conwell, in Semiconductors and Semimetals: Highly Conducting Quasi-One-Dimensional Organic Crystals, ed. E. M. Conwell, Academic Press, New York, 1988, vol. 27, pp. 1–27.
9. W. E. Hatfield, W. E. Estes, W. E. Marsh, M. W. Pickens, L. W. ter Haar and R. R. Weller, in Linear Chain Compounds, ed. J. S. Miller, Plenum Press, New York, 1983, vol. 3, p. 43.
10. J. C. Bonner and M. E. Fisher, Phys. Rev. A, 1964, 135, 640.
11. J. C. Bonner and H. W. J. Blöte, Phys. Rev. B, 1982, 25, 6959.
12. W. E. Hatfield, J. Appl. Phys., 1981, 52, 1985.
13. F. L. Pratt, W. Hayes, M. Kurmoo and P. Day, Synth. Met., 1988, 27, 439.
14. M. Kurmoo, P. Day, A. M. Stringer, J. A. K. Howard, L. Ducasse, F. L. Pratt, J. Singleton and W. Hayes, J. Mater. Chem., 1993, 3, 1161.