BOIMPYs: Rapid Access to a Family of Red-Emissive Fluorophores and NIR Dyes.

A fundamental, highly fluorescent, and easily accessible scaffold derived from the BODIPY core is reported. The use of benzimidazole as a bridging ligand at the meso position enables the binding of two BF2 units to provide sufficient rigidity and enhanced electron-withdrawing strength. Absorption and emission events thus take place in the red (λ≈600 nm); the fluorescence quantum yields can reach unity (0.96) and show little dependence on solvent polarity. The synthetic route was shortened to two steps starting from commercially available precursors while the preparation is modular and tolerates various pyrrole and benzimidazole moieties. Fluoride replacement by propynyl groups, various halogenations, as well as Knoevenagel-type condensations were applied to extend the versatility of these new photostable fluorophores, which we termed BOIMPYs.