α-Fused dithienyl BODIPYs synthesized by oxidative ring closure

Both symmetrical and unsymmetrical α-fused dithienyl-BODIPY dyes have been prepared by oxidative ring closure induced by anhydrous FeCl3. Extension of the π-system in the fused BODIPY leads to a progressive shift to 579 and 665 nm respectively for the absorption wavelength maxima of the mono- and difused dyes relative to the unfused species (λ(abs) = 502 nm). Linking such dyes to an NIR emitting module provides a panchromatic chromophore with a large absorption cross section in the visible range associated with efficient intramolecular cascade energy transfer.