Synthesis, Photophysical Properties, and Primary Biological Characteristics of Meso-pyrazole-substituted BODIPY...

In the present study, two novel meso-pyrazole-substituted BODIPY platforms were synthesized by an acid-catalysed condensation reaction of pyrazole-4-carbaldehydes with 2,4-dimethylpyrrole, followed by complexation with BF₃·OEt₂. Comprehensive investigations were carried out to characterize the structural, photophysical, and biological properties of the target BODIPY compounds. These investigations included structural elucidation through mass spectrometry and NMR spectroscopy, as well as spectroscopic analyses such as UV-Vis absorption, fluorescence emission, and quantum yield measurements. Compounds exhibited very similar absorption and fluorescence behaviors, with only minor shifts in their absorption and fluorescence maxima, indicating that minor structural differences had little influence on the overall photophysical properties. However, the fluorescence quantum yields of compounds 3 and 4 were found to be 0.82 and 0.33, respectively, despite their very similar absorption and emission characteristics. Additionally, primary biological characterizations were performed particularly regarding the biological importance of the coumarin unit. Accordingly, both novel compounds exhibited cytotoxicity against the human colorectal cancer cell line, with an inhibitory concentration 50 (IC50) value of 47.46 ± 3.69 and 83.56 ± 2.40 mg/ml. Moreover, the toxicities were proved to be a result of whether apoptosis or necrosis. Furthermore, the compounds were able to internalize into the cells, enabling live cell imaging. Notably, the coumarin-containing compound displayed aggregation-dependent alterations in photophysical properties with dual fluorescence, confirming the previous reports. Hence, developing such compounds is a feasible approach to comprehensively elucidate the photochemistry of BODIPY modulations and propose new application areas.