Effect of AIE substituents on the fluorescence of tetraphenylethene-containing BODIPY derivatives.

A series of BODIPY derivatives with tetraphenylethene (TPE) moieties were designed and synthesized. The effect of positions and numbers of substitution groups on the fluorescence of the BODIPYs was investigated. Theoretical calculation and single crystal structures proved that the TPE substitution groups on the 8-position of BODIPY contributed little to the conjugation, but benefited the aggregated state emission. On the other hand, the substitutions on the 3- or 5-position of BODIPY through vinyl bridges increased the conjugation length, and generated big coplanar π-conjugated structures with poor aggregated state emission. The compound with bright aggregated state emission has been further fabricated into biocompatible fluorescent nanoparticles and used as effective fluorescent contrast agents for intracellular imaging.