An efficient synthesis of symmetrical oligothiophenes: Synthesis and transport properties of a soluble sexithiophene derivative

We report a new approach for the synthesis of symmetrical oligothiophenes based on a highly efficient palladium-catalyzed Ullmann coupling reaction. This synthetic route enables the simple preparation of substituted oligothiophenes with a wider range of functionalities and in higher yield compared to previously reported syntheses. We demonstrate our procedure by preparing a novel, highly soluble alpha,omega-substituted sexithiophene, dibutylphosphonate-alpha-sexithiophene (DBP-alpha-6T). We present spectroscopic characterization of this compound in solution and solution cast thin films. Thin film transistors (TFTs) fabricated using solution cast thin films of DBP-alpha-6T as the p-type semiconducting channel have high on/off ratios, demonstrating the utility of this synthetic approach in the preparation of highly pure materials for solution-deposited organic electronic devices.