Tetrakis(methyltelluro)tetrathiafulvalene (TTeC₁TTF), a high-mobility organic semiconductor

Abstract

We have found a class of highly conductive single-component organic semiconductors; the tetrakis(alkylthio)tetrathiaful-valenes, and have given these systems the descriptive title of 'molecular fastener'^1,2. In a programme to synthesize single-component molecular assemblies with high conductivity, we then discovered a new organic semiconductor, tetrakis(alkyltel-luro)tetrathiafulvalene, of electrical resistivity 8.1 x 10⁴ Ωcm, having high charge mobility, 20–30 cm² V^–1 s^–1. We explain this unusually low resistivity in terms of molecular packing and stacking manner within the crystal. The central skeleton of this compound, tetratelluro-tetrathiafulvalene moiety (C⁶Te⁴S⁴), is almost planar and is regularly stacked in the form of column. Along the stacking axis, tellurium atoms in neighbouring columns come close each other and form zigzag chains. The distance between those two Te atoms is 3.644(2) Å, which is significantly shorter than van der Waals distance (4.12 Å). It is expected that zigzag chalcogen chains formed from quasi-covalent bonds.