We took advantage of the chemoselective meso-functionalization of 2,3,5,6-tetrabromo-8-methylthioBODIPY 6 to prepare a series of 2,3,5,6-tetrabromo-8-arylBODIPY derivatives suitable for SNAr substitution reactions with phenols exclusively at positions 3 and 5. Pd(0)-catalyzed intramolecular arylation reaction ensued on the remaining brominated positions 2 and 6 to give a new family of benzofuran-fused BODIPY dyes. This method utilizes readily available starting materials and allows for the preparation of the title compounds with excellent functional group tolerance. Moreover, it was demonstrated that the methodology described herein is amenable for the incorporation of biomolecules. The photophysical and lasing properties of the benzofuran-fused BODIPY dyes were thoroughly analyzed with the aid of electrochemical measurements and quantum mechanical simulations. These dyes show bright and intriguing emission (both fluorescence and laser) toward the red edge of the visible spectrum with remarkable tolerance under strong and continuous irradiation.

Serotonin (5-HT) modulates key aspects of the immune system. However, its precise function and the receptors involved in the observed effects have remained elusive. Among the different serotonin receptors, 5-HT plays an important role in the immune system given its presence in cells involved in both the innate and adaptive immune responses, but its actual levels of expression under different conditions have not been comprehensively studied due to the lack of suitable tools. To further clarify the role of 5-HT receptor in the immune system, we have developed a fluorescent small molecule probe that enables the direct study of the receptor levels in native cells. This probe allows direct profiling of the receptor expression in immune cells using flow cytometry. Our results show that important subsets of immune cells including human monocytes and dendritic cells express functional 5-HT and that its activation is associated with anti-inflammatory signaling. Furthermore, application of the probe to the experimental autoimmune encephalomyelitis model of multiple sclerosis demonstrates its potential to detect the specific overexpression of the 5-HT receptor in CD4+ T cells. Accordingly, the probe reported herein represents a useful tool whose use can be extended to study the levels of 5-HT receptor in ex vivo samples of different immune system conditions.

Herein we report on a straightforward access method for boron dipyrromethene dyes (BODIPYs)-coumarin hybrids linked through their respective 8- and 6- positions, with wide functionalization of the coumarin fragment, using salicylaldehyde as a versatile building block. The computationally-assisted photophysical study unveils broadband absorption upon proper functionalization of the coumarin, as well as the key role of the conformational freedom of the coumarin appended at the meso position of the BODIPY. Such free motion almost suppresses the fluorescence signal, but enables us to apply these dyads as molecular rotors to monitor the surrounding microviscosity.