Synthesis of Soluble Dinaphtho[2,3- b:2′,3′- f]thieno[3,2- b]thiophene (DNTT) Derivatives: One-Step Functionalization of 2-Bromo-DNTT

For developing dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) derivatives as solution processable organic semiconductors, we synthesized 2-brominated DNTT (Br-DNTT) as a common precursor to 2-substituted DNTT derivatives. The synthesis of Br-DNTT features chemoselective metalation and cross-coupling reactions that enable us to keep the 2-bromo group intact from the starting material, 2-bromo-6-methoxynaphthalene, to Br-DNTT. We demonstrated one-step functionalization of Br-DNTT by various palladium- and copper-catalyzed cross-coupling reactions to introduce a variety of substituents, including ethynyl, aryl, heteroaryl, alkyl, alkoxy, and alkylthio groups, in yields of 73 to 98%. The resulting 12 examples of 2-substituted DNTT derivatives, which have bulky or flexible solubilizing groups, have improved solubilities of up to 200 times the solubility of unsubstituted DNTT. Some of the soluble 2-substituted DNTT derivatives were applied to the solution-processed fabrication of organic field-effect transistor (OFET) devices. Most of the OFET devices exhibited average hole mobilities in the order of 10^-1 to 10^-2 cm² V^-1 s^-1. Among the DNTT derivatives, the one substituted with 4-(2-(2-methoxyethoxy)ethoxy)butyl group has the highest solubility of 8.45 g L^-1 and also exhibited the highest average hole mobility of 0.28 cm² V^-1 s^-1 in the OFET devices.