EXCITATION WAVELENGTH DEPENDENCE OF PROTOTROPIC DISSOCIATION AND TAUTOMERISM OF SALICYLAMIDE IN THE LOWEST EXCITED SINGLET-STATE

Abstract—The fluorescence spectra of salicylamide in cyclohexane, ethanol and at different pH in water were studied. The short and long wavelength fluorescences observed in the organic solvents originate from emissions of a weakly or non‐intramolecularly hydrogen bonded conformer and from phototautomerization of a strongly intramolecularly hydrogen bonded conformer, respectively. Evidence for at least 2 conformers in the ground state exists in the excitation wavelength dependence of the ratio of short wavelength to long wavelength emission. In water, prototropic dissociation of the phenolic group of salicylamide in the lowest excited singlet state also shows an excitation wavelength dependence, indicating that the weakly or non‐intramolecularly hydrogen bonded conformer in water is predominately responsible for photodissociation. Copyright © 1979, Wiley Blackwell. All rights reserved