Synthesis, characterization and photophysical properties of meso-indole-boron-dipyrromethene derivatives and their cell imaging and viscosity sensing

Based on the molecular design and structural modification of boron-dipyrromethene (BODIPY), two new BODIPY derivatives with meso-substituted functional indole moieties were successfully prepared. These new compounds were characterized by NMR, HAMS and FTIR, exhibiting the different UV-vis and PL spectral phenomena because of their varied molecular structures in various solvents and different degrees of negative solvatochromism. Theoretical calculations and CV results show that the substituted NO2 group at 5-position of indole is favorable for increasing the oxidation potential of the molecules, while the NH2 group is the opposite. These two BODIPY derivatives have different sensitivities to pH changes, and can be appropriately applied as cell imaging materials due to their good physical chemical characteristics and excellent biocompatibility. In particular, the fluorescence characteristics of BODIPY derivative with the substituted NH2 group at 5-position of indole show a good solvent viscosity dependence, highlighting its potential application for testing the intracellular viscosity changes of the living cell in disease diagnosis.