Kinetics of excited-state proton-transfer reactions and proton-induced fluorescence quenching of 1-naphthol (1N) and 2-octadecyl-1-naphthol (2O1N) in micellar solutions of cetyltrimethylammonium bromide (CTAB), polyoxyethylene(23) lauryl ether (Brij 35), and sodium dodecyl sulfate (SDS) was studied by using stationary and time-resolved fluorescence techniques. The ground-state acidity constant of 2O1N in cationic micelles of CTAB was found to be significantly smaller than that of the parent compound (ΔpK = 0.5). However, similar rate and equilibrium constants of the protolytic dissociation were obtained for 1N and 2O1N in the singlet excited state. Effects of nonionic micelles of Brij 35 closely resemble those of CTAB. In anionic micelles of SDS, the protolytic photodissociation was much slower for 2O1N than for 1N. The protonation rate for the excited anions in micellar solutions increases by approximately 2 orders of magnitude in the series CTAB, Brij 35, SDS. Excited-state kinetics was rationalized within the framework of a pseudophase model, which included micellar effects on the proton-transfer equilibrium and interfacial diffusion of hydronium ions. The electrostatic surface potential of charged micelles was estimated from the acidity constants of naphthols.

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The bifunctional photoacid ω-(2-hydroxynaphthyl-1)-decanoic acid (1S2N) takes part both in intramolecular excited-state proton transfer (ESPT) to the anion of a fatty acid and in intermolecular ESPT in the presence of a water solvent. Excited-state intra- and intermolecular proton transfer of 1S2N was investigated in homogeneous ethanol/water solution and in micellar solutions of various surfactants. The interfacial potential of micelles was changed by using cationic (CTAB), non-ionic (Brij-35) and anionic (SDS) surfactants. With the decrease of the interfacial potential, the protolytic photodissociation of naphthol and the diffusion-controlled intramolecular ESPT to carboxylic anion were suppressed.