The interaction of aliphatic amines with safranine T in aqueous solution

Encinas M.V.; Previtali C.M.; Gehlen M.H.; Neumann M.G.

Abstract

The photophysics of the excited states of safranine T and its reactions with aliphatic amines were studied in aqueous solution. The fluorescence lifetime of the singlet state was found to be 1.3 ns at 20 °C in water, and increases in non-hydroxylic solvents. This state is quenched by trialkylamines with nearly diffusional rate constants. In addition to the intense absorption of the monoprotonated form of the triplet state at 820 nm, a weaker absorption at 420 nm was detected. The non-protonated form also has a residual absorption at 820 nm. The lifetime of the non-protonated triplet was found to be around 15 ?s. The monoprotonated triplet state of the dye is quenched by amines with rate constants of about 1 × 109 M -1 s -1, too high to be ascribed to a charge transfer mechanism. Similar to the reaction in organic solvents, this reaction proceeds by a proton transfer mechanism, leading to the non-protonated form of the triplet state. This form is then quenched by another amine molecule to give the corresponding semireduced species.

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Título de la Revista: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A: CHEMISTRY
Volumen: 94
Número: 2-3
Editorial: ELSEVIER SCIENCE SA
Fecha de publicación: 1996
Página de inicio: 237
Página final: 241
URL: http://www.scopus.com/inward/record.url?eid=2-s2.0-0030574776&partnerID=q2rCbXpz