Synthesis and properties of thieno[3,2-b]thiophene appended triarylamine radical cations: Near-infrared absorbing dye with absorption beyond 1400 nm.

Two triphenylamines with thieno [3,2- b ] thiophene units were designed and synthesized. The radical cations obtained by the one-electron oxidation of these amines show a significant absorption in the near-infrared region. In particular, the derivative with three hexyl groups has excellent solubility, and its radical cation has a maximum absorption wavelength above 1400 nm. DFT calculations support these experimental results. A novel design strategy for NIR-II dyes is described. Two triphenylamines with thieno [3,2- b ] thiophene units were designed and synthesized. The radical cation with long-chain hexyl groups was stable in solution and showed a maximum absorption at 1430 nm. [Display omitted] • Novel triphenylamine with three thieno[3,2- b ]thiophenes. • The derivative with hexyl groups has excellent solubility. • The radical cation with hexyl groups was stable at room temperature in solution, and showed an absorption at 1430 nm. • Near-infrared absorbing dyes with high solubility and absorption in longer wavelength regions. [ABSTRACT FROM AUTHOR]