Trianionic 1,3,2-Dioxaborine-Containing Polymethines: Bright Near-Infrared Fluorophores.

Trianionic polymethines of the A'-π-A-π-A-π-A' type comprising dioxaborine rings (A) and different electron-accepting end groups (A') have been synthesized. The obtained dyes absorb and emit light in the near-infrared region with remarkably high molar attenuation coefficients (ϵ up to 495 000 M  cm in DMF) and fluorescence quantum yields (Φ up to 0.73 in DMF).