Near-infrared aza-BODIPYs bearing tetraphenylethylene: Synthesis, photophysical studies, and cell imaging application

We provide a simple method to synthesize tetraphenylethylene-modified aza-BODIPY dyes (AZB-TPE1 and AZBTPE2) with aggregation-enhanced emission. Single-crystal X-ray method, electrochemical experiments, and TDDFT calculations were used to understand more about their electronic and photophysical properties. The intramolecular energy transfer between the TPE donor and the aza-BODIPY acceptor was observed from both dyes, with 84-97% energy transfer efficiencies and large pseudo-Stokes shifts of 395 - 406 nm. Aggregation studies in THF/water solution showed increased fluorescence in the aggregated form. X-ray crystal structure of AZB-TPE2 suggested the reduction of intermolecular pi-pi interactions between the structures. Finally, these NIRemitting particles with superior water dispersion and biocompatibility demonstrated amazing features in bioimaging applications.