Ground- and excited-state intramolecular proton transfer in 3,5-dibromosalicylic acid

The existence of both ground- and excited-state proton transfer equilibrium between the enolic and keto tautomers. of 3,5-dibromosalicylic acid has been investigated in aqueous solution using electronic absorption and luminescence emission spectroscopies, together with ab initio and semiempirical MO/CI calculations. The compound provides an example of a room temperature phosphorescence triplet-state emission from a phototautomer (ketonic) form. The interference from radiationless paths, which may in principle avoid the observation of the phosphorescence signal, was overcome by using a protective micellar medium and the presence of an external heavy atom. (C) 2002 Elsevier Science B.V. All rights reserved.