SOLUTE-SOLVENT INTERACTIONS IN THE GROUND-STATE AND IN ELECTRONIC EXCITED-STATES - DIPOLAR APROTIC TO POLAR PROTIC SOLVENT BLUE SHIFT OF SOME ANILINES AND PHENOLS

The long-wavelength transition of some anilines, phenols, and their nitro derivatives was found to be blue shifted on transfer from dimethylformamide to methanol solvent. The enthalpies of transfer of the Franck-Condon excited states were then determined by combining calorimetric and spectroscopic data. It was found that enthalpies of transfer of the Franck Condon excited states were uniformly endothermic into the hydrogen-bonding solvent. An estimate of the solvent transfer enthalpies of the corresponding relaxed excited states was made from fluorescence, absorbance, and calorimetric data. A comparison of the solvent transfer enthalpies of the ground state, the Franck-Condon excited state, and the relaxed excited state was used to evaluate the specific solvation mechanisms causing the blue shift. © 1979, American Chemical Society. All rights reserved.