α-Fused Dithienyl BODIPYs Synthesized by Oxidative Ring Closure

Both symmetrical and unsymmetrical alpha-fused dithienyl-BODIPY dyes have been prepared by oxidative ring closure induced by anhydrous FeCl3. Extension of the pi-system in the fused BODIPY leads to a progressive shift to 579 and 665 rim respectively for the absorption wavelength maxima of the mono- and difused dyes relative to the unfused species (lambda(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.