Near-infrared absorption of a benzothiophene-appended triphenylamine radical cation: A novel molecular design of NIR-II dye

Abstract A triphenylamine with three benzothiophene rings was designed and successfully synthesized in 87% yield. The compound showed absorption at 386 nm and blue emission at around 442 nm, with a fluorescence quantum yield of 0.57. The compound showed high thermostability. The radical cation obtained by one-electron oxidation was stable in solution and showed a significant absorption in the NIR-II region (λmax = 1213 nm). DFT calculations confirmed the experimental data.