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A series of new organic semiconductors based on s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione was successfully synthesized and characterized. The electron withdrawing carbonyl group lowers the LUMO energy levels, leading to increased electronegativities, which is beneficial for high photo-stability in air. The n-alkyl substituted compounds, 1c and 1d, crystallize with the rigid coplanar systems packed into slipped face-to-face π-stacks. Interestingly, 1c and 1d also show liquid crystalline behaviors, which give highly ordered molecular packing over large area.

Two new azapentacene derivatives 9,10-dibromo-6,13-bis(triisopropylsilylethynyl)-1-azapentacene (a) and 8,9,10,11-tetrachloro-6,13-bis(triisopropylsilylethynyl)-1-azapentacene (b) were synthesized, and their FET properties were investigated. Compound b exhibits high and balanced ambipolar transport properties, with the hole and electron mobilities reaching up to 0.12 and 0.14 cm(2) V(-1) s(-1), respectively. This work suggests that chlorination to the N-heteropentacene framework is an efficient way for producing high performance ambipolar organic semiconductors.