Novel BODIPY preparations from sterically hindered pyrroles. Synthesis and photophysical behavior in solution, polystyrene nanoparticles, and solid phase

Trimesityl-BODIPY (TMB), a new derivative of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene belonging to fluores-cent nanostructures series, was synthesized from the corresponding pyrrole by the Trofimov reaction. This reaction was also employed to obtain 2-[2.2]paracyclophanylpyrrole from 5-acetyl[2.2]-paracyclophane. The spectral properties of TMB have been investigated in dichloromethane, nanolatex (polystyrene) films prepared by rapid solvent evaporation, and microcrystals. Comparative analysis of TMB properties with those of mesityl-BODIPY (MB) was performed. TMB was prepared to minimize pi-pi interactions in order to preserve luminescence in the aggregate state. Both fluorophores were shown to form fluorescing aggregates in the amorphous state (film). Fluorescence spectra (extinction and lifetime) were also studied. In crystal, MB shows a weaker fluorescence, while TMB behaves as a single fluorescing aggregate with a lifetime of 9.5 ns.