Tunable blue-emitting fluorophores—benzo[1,2-b:4,3-b′]dithiophene and trithia[5]helicene end-capped with electron-rich or electron-deficient aryl substituents

Light-emitting fluorophores 1-10b based on aryl substituted benzo1,2-b:4,3-b′]dithiophenes (BDT) and trithia5]helicenes (T5H) have been synthesized using various combinations of Suzuki coupling, the Wittig, or McMurry reaction, and subsequent photocyclization of the dithienylethenes thus obtained. Photophysical properties of the helical compounds end-capped with different electron-rich and electron-deficient aryl moieties thus resulting were evaluated. Photocyclization of a dithienylethene derivative 10a was investigated, and the X-ray crystal structure of dinaphthyl-substituted BDT (4) was obtained. With this series of compounds 1-10b, we demonstrate that the optical properties of all of the new compounds, and by extension many conjugated materials, can be tuned over the entire blue range (400-480 nm).