Quantitative study of the substituent effects on the electronic absorption and fluorescence spectra of coumarins

Because of their important fluorescence properties, coumarins are widely applied in sensing devices. In this paper, the electronic inductive, mesomeric, and electromeric substituent effects on the electronic absorption and fluorescence spectra of 11 substituted coumarins, including NH2, NMe2, NEt2, OH, CF3, CH3, COOH, Cl, and Br substituents, have been quantitatively studied by means of structure‐reactivity relationships. We have applied the Hammett, Brown‐Okamoto, and Yukawa‐Tsuno correlations to the coumarins electronic absorption and fluorescence spectra wavenumbers and Stokes shifts. The Stokes shift of coumarins decreased when the electron‐donor inductive/mesomeric power of the substituent increased. This Stokes shift decrease was more pronounced when the solvent polarity increased, which might be explained by the electromeric effect increase.