Electronegative Oligothiophenes for n-Type Semiconductors:  Difluoromethylene-Bridged Bithiophene and Its Oligomers

The synthesis of difluoromethylene-bridged bithiophene and its oligothiophenes are reported. The spectroscopic and electrochemical measurement as well as X-ray analyses unambiguously revealed that the difluoromethylene bridge largely contributes to keeping planarity between the thiophene rings and lowering the LUMO level. The perfluorohexyl-substituted quaterthiophene derivatives showed n-type semiconducting behavior with field-effect electron mobilities up to 0.018 cm² V^-1 s^-1.