Spectral and Quantum Mechanical Characterization of 3-(2-Benzothiazolyl)-7-(Diethylamino) Coumarin (Coumarin 6) in Binary Solution

Absorption and fluorescence spectra of 3-(2-benzothiazolyl)-7-(diethylamino) coumarin in various solvents were recorded to characterize intermolecular interactions. The contributions of each interaction to the total spectral shifts were estimated. The properties of coumarin 6 were calculated using density function theory with the hybrid functional B3LYP level theory combined with 6-311 + G basis set. The excited state dipole moment was calculated from the variation of spectral shifts in absorption and fluorescence with solvent permittivity and refractive index using the Lippert–Mataga, Bakhshiev, and Kawski–Chamma–Viallet equations.