J. Phys. IV France
Volume 114, April 2004
Page(s) 431 - 437

J. Phys. IV France
114 (2004) 431
DOI: 10.1051/jp4:2004114102

Tetrathiapentalene-type donors containing (thio)pyran-4-ylidene as a promising $\pi $-electron framework for multi-dimensional molecular conductors

Y. Misaki1, T. Kaibuki1, K. Takahashi1, T. Nakayashiki1, K. Tanaka1, T. Kawamoto2 and T. Mori2

1  Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
2  Department of Organic Materials, Tokyo Institute of Technology, O-okayama, Tokyo 152-8552, Japan

The conducting materials based on 2-(1,3-dithiol-2-ylidene)-5-(pyran-4-ylidene)-1,3,4,6-tetrathiapentalene (PDT-TTP) and its thiopyran and/or selenium analogues have been developed. The ethylenedithio derivative (ET-PDT) affords 4:1 salt with PF 6- anion (ET-PDT) 4PF 6(cn) (cn = 1-chloronaphthalene). It has the so-called $\lambda $-type array of the donors with quasi one-dimensional electronic structure due to strongly tetramerized stack. On the other hand, (TM-TPDS) 2AsF 6 adopt the "windmill type" array of the donors. In this salt, relatively large side-to-edge interactions stabilize their electronic structure, while effective side-by-side interaction is inhibited by methythio groups projected along the molecular short axis. In contrast, edge-to-edge interactions are dominant in (SM-PDT)PF 6(PhCl) x through selenium-selenium contacts along the molecular long axis. (ET-PDT) 4PF 6(cn) shows metallic conductivity down to 1.5 K, while (TM-TPDS) 2AsF 6 is an organic metal exhibiting MI transition at 100 K. On the other hand, (SM-PDT)PF 6(PhCl) x is a semiconductor with relatively high conduuctivity of $\sigma _{rt} = 4.8$ S cm -1 in spite of 1:1 composition. Key words. tetrathiapentalene - X-ray structure analysis - electrical conductivity.

© EDP Sciences 2004