Approaching the Integer‐Charge Transfer Regime in Molecularly Doped Oligothiophenes by Efficient Decarboxylative Cross‐Coupling

A library of symmetrical linear oligothiophene was prepared employing decarboxylative cross‐coupling reaction as the key transformation. Thiophene potassium carboxylate salts were used as cross‐coupling partners without the need of co‐catalyst, base, or additives. This method demonstrates complete chemoselectivity and is a comprehensive greener approach compared to the existing methods. The modularity of this approach is demonstrated with the preparation of discreet oligothiophenes with up to 10 thiophene repeat units. Symmetrical oligothiophenes are prototypical organic semiconductors where their molecular electrical doping as a function of the chain length can be assessed spectroscopically. An oligothiophene critical length for integer charge transfer was observed to be 10 thiophene units, highlighting the potential use of discrete oligothiophenes as doped conduction or injection layers in organic electronics applications. Symmetrische lineare Oligothiophene sind wichtige organische Modell‐Halbleiter. Eine Bibliothek solcher Oligothiophene wurde durch eine decarboxylierende Kreuzkupplungsroute synthetisiert. Diese Verbindungen ermöglichen es, die kritische Oligomerlänge für den ganzzahligen Ladungstransfer bei molekularer Dotierung zu erforschen und damit die fundamental unterschiedlichen Dotierungsphänomene von Oligo‐ und Polythiophenen miteinander in Beziehung zu setzen.