3-Perfluoroalkylated fluorescent coumarin dyes: rational molecular design and photophysical properties†

Owing to their excellent fluorescence properties, coumarin derivatives have diverse applications in phototherapy and optoelectronics. Coumarin derivatives with a trifluoromethyl group at the 4-position have been extensively investigated; however, studies on the photophysical properties of fluorescent 3-trifluoromethylated coumarins in solution and in the solid state are rare. Hence, in this study, the photochemical properties of a coumarin derivative incorporating a promising electron-withdrawing fluoroalkyl group at the 3-position in solution and in the crystal form were investigated in detail by absorption and fluorescence spectral measurements, density functional theory and time-dependent density functional theory calculations, and single crystal X-ray structure analysis. The aim was to verify the reasons for its excellent fluorescence emission in solution and in the crystal form. These molecular compounds are expected to have potential applications as coumarin fluorophores in fluorescent emission probes and electronic light-emitting devices.