Synthesis of 2,5-bis(9H-fluoren-9-ylidene)-2,5-dihydrothiophene derivatives and a systematic study of the substituent effect

Abstract

2,5-Bis(9H-fluoren-9-ylidene)-2,5-dihydrothiophene (ThBF) was potentially important for utilization as an organic semiconductor material. However, the study of the structure–property relationship for this compound was very limited due to its harsh synthesis. Here, we reported the synthesis of a series of ThBF derivatives B1–B9 using a two-step synthetic route involving a Lewis acid-promoted Friedel–Crafts reaction followed by an oxidation process. Compared to conventional methods, the promoted synthetic route was much milder, providing the feasibility for the introduction of halogen atoms. Subsequently, the substituent effects on their thermal, opto-physical, and electro-chemical properties as well as the structure and energy information of ThBFs were systematically explored by experimental and theoretical studies.