Excited-State Prototropic Reactivity in Salicylamide and Salicylanilide

Article abstract of DOI:10.1021/ja00543a003

Steady-state fluorescence measurements have suggested the existence in both salicylamide and salicylanilide of "open" and "closed-ring" ground-state conformers which give rise to different emission upon excitation.Excitation of the "closed-ring" conformer leads to intramolecular proton transfer across the preexisting H bond to give the excited zwitterion.Excitation of the "open-ring" conformer gives rise to both emission from an uncharged excited state and emission from an excited phenolate species, the relative intensities depending on the pH.Laser/streak kamera measurements have yielded the phenolate and zwitterion lifetimes and indicate that the protolytic reactions are extremely fast.