Bulky Phenylalkyl Substitutions to Bisthienoisatins and Thienoisoindigos

• Published in: Crystal growth & design 2020-05, Vol.20 (5), p.3293-3303
• Main Authors: Yoo, Dongho, Kohara, Akihiro, Ashizawa, Minoru, Kawamoto, Tadashi, Masunaga, Hiroyasu, Ohta, Noboru, Matsumoto, Hidetoshi, Mori, Takehiko
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.0c00087

In order to investigate the effects of bulky substituents on the crystal structures and packing modes, N-benzyl (Bn) and N-2-phenylethyl (EtPh) substituents are introduced in bisthienoisatin (BTI), thienoisoindigo (TIIG), and dibenzothienoisoindigo (DBTII). These molecules maintain uniform stacking structures, though EtPh-BTI has a two-dimensional slipped-herringbone structure. The benzyl groups are largely distorted from the molecular core, and thin films of Bn-TIIG and Bn-DBTII show poor quality due to the two kinds of molecular orientations. In contrast, the 2-phenylethyl-substituted molecules enable suitable molecular packing owing to the ethylene spacer and show relatively good thin-film qualities as well as much improved transistor properties. The BTI derivatives show only electron transport, but other compounds exhibit ambipolar transistor properties. In particular, EtPh-TIIG and EtPh-DBTII show maximum hole mobilities of about 0.04–0.05 cm2 V–1 s–1 together with moderate electron mobilities.