A highly efficient palladium-catalyzed direct C-H functionalization/annulation of BODIPYs with alkynes has been developed for the first time to construct a series of unsymmetrical benzo[ b]-fused BODIPYs from readily available starting materials. These unsymmetrical benzo[ b]-fused BODIPYs exhibit remarkably red-shifted emissions and larger Stokes shifts than classical BODIPY dyes. Cell imaging experiments and cytotoxicity assays demonstrate that BODIPYs 4c and 4d have specific lysosome-labeling capacities, turn-on fluorescence emissions in cells, and low cytotoxicity.

The direct C-H activation of electron-deficient aza-BODIPYs has been effectively achieved via a concise and inexpensive Cu(ii)-promoted oxidative C-H/C-H coupling approach. The resulting indole-aza-BODIPY 6b covers a broad spectrum of 429-900 nm with a FWHM of 294 nm in solution and covers a UV-vis-NIR region up to 1100 nm in film.