Planar Heptathienoacenes Based on Unsymmetric Dithieno[3,2-b:3′,4′-d]thiophene: Synthesis and Photophysical Properties

The unsymmetric dithieno[3,2-b:3',4'-d]thiophene (ts-DTT) was efficiently synthesized, and two novel heptathienoacenes with linear and bull's horn shapes were designed and prepared via different ring cyclization connection manners. All intermediates and aimed heptathienoacenes were fully characterized by H-1 NMR, C-13 NMR, and HRMS. Their UV-vis absorption behavior, fluorescence, and electrochemical properties are characterized. In addition, DFT quantum calculation was employed to further understand the electron distribution and the origin of the absorption bands.