Hetero-analogues of Hückel degenerate systems and related compounds: preparation of thienyl-substituted fulvalene and electron-donating tetrathiafulvalene vinylogues and conductive complexes

Abstract

1,4-Bis[6-(2-thienyl)fulven-6-yl]benzene 9 has been prepared as a model of the six-fold Huckel HOMO-degenerate tetracyclopentadienylideneethane biradical vinylogue. This extended dithienylfulvalene 9 was reduced reversibly to the dianion. Attempted preparation of other dithienylsubstituted extended fulvalenes 4 and 8 are described. Attempted preparation of dithiolylidenedithienylethane 17 gave only the monocondensed products 22 and 24. An attempted preparation of the vinylene analogue 18 from the dithienylbutenedione 12 gave, instead, the unexpected products 25, 26 and 27. Thus, compound 18 was prepared via the cyclopentadiene cycloadduct 30. The phenylene analogue 19 was prepared from 1,4-dithenoylbenzene 15. The extended tetrathiafulvalenes 18 and 19 were found to be good electron donors. The nonplanar vinyleneTTF 18 formed conductive CT complexes with TCNQ and iodine. The outcome of these studies are discussed.