Organic Field-Effect Transistors Based on Alkyl-Terminated Tetrathiapentalene (TTP) Derivatives

A study was conducted to analyze a new skeleton of organic field-effect transistors (OFET) materials, tetrathiapentalene (TTP), the compounds of which have considerably higher oxidation potentials than tetrathiafulvalene (TTF), which is expected to be advantageous to device stability. Compounds 1 and 2 were synthesized by phosphite-mediated coupling reactions of the starting material, 3 and 4, which were prepared by the Wittig reaction between a TTP-based phosphonate and the ketone. The alkyl-capped TTP molecules were obtained by a phosphite-mediated contracting-coupling reaction, in which two TTP units merged into one. Compound 2 is a high-performance OFET material, the relatively high oxidation potential of which is responsible for both stability and small threshold voltage. It is also notable that introduction of the outer ring system entirely changes the crystal and thin-film structures, and this is important in achieving the desired OFET properties.