Extended Benzene-Fused Oligo-BODIPYs: In Three Steps to a Series of Large, Arc-Shaped, Near-Infrared Dyes

We present a straightforward, three-step synthesis engaging an oligomerization and subsequent one-pot oxidation step to form fully conjugated, benzene-fused oligo-BODIPYs from simple BODIPY precursors. FeCl3 serves as an efficient, bifunctional oxidant for a (multiple) cyclization/desaturation process, applied to ethylene-bridged dimeric, trimeric and oligomeric species to transform linking ethano units into stiff benzene fusions between unsubstituted beta-positions of each BODIPY unit. The structural integrity was verified by X-ray crystallography, and all target compounds were studied in detail by photophysical, electrochemical and computational means. The main S-1 excited state gradually converges to a structure-specific excitation limit, displaying a strong shift of the absorption event from about 500 nm (BODIPY monomer) to 955 nm (octamer) with attenuation coefficients up to ca. 500 000 M-1 cm(-1).

Automated summary

A straightforward three-step synthesis was presented to form fully conjugated benzene-fused oligo-BODIPYs from simple BODIPY precursors, with the structural integrity confirmed by X-ray crystallography. The main S-1 excited state showed a strong shift in absorption event from BODIPY monomers to octamers.