Conformation-Restricted Partially and Fully Fused BODIPY Dimers as Highly Stable Near-Infrared Fluorescent Dyes

A set of highly stable conformation-restricted partially and fully fused BODIPY dimers (α,β-cyclohexadiene-fused and α,β-benzene-fused dimers) were synthesized from a one-pot condensation of 2-formylpyrroles with α,β-cyclohexadiene-fused bipyrrole 3. Effective expansion of π-conjugation over these fused BODIPY dimers was observed by X-ray analysis, density functional theory (DFT) calculations, and electrochemical and optical measurements, as demonstrated by their strong absorption and emissions in the near-infrared (NIR) range (650 to 820 nm).