Solution-Processed and Air-Stable n‑Type Organic Thin-Film Transistors Based on Thiophene-Fused Dicyanoquinonediimine (DCNQI) Deriatives

π-Conjugated systems 2a and 2b containing thiophene-fused DCNQI with long alkyl and trifluoromethylphenyl groups were synthesized as potential active materials for solution-processed and air-stable n-type organic thin-film transistors (OTFTs). The electrochemical measurements revealed that the lowest unoccupied molecular orbital (LUMO) of the compounds have an energy level less than −4.0 eV, indicating air stable n-type materials. The long alkyl groups endowed the compounds good solubility and solution-processability. X-ray diffraction measurements revealed the difference of the molecular arrangement depending on the alkyl groups, which were also observed in the UV–vis absorptions of the films. A relatively good mobility up to 0.003 cm² V^–1 s^–1 for 2a by spin-coating was obtained with good air stability.