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(6). The dependence of absorption and fluorescence spectral characteristics upon acidity has allowed us to characterize four species, namely, the anion (A), the neutral molecule (N), the cation (C), and the dication (DC), for molecules 2 and 3 . Molecules 4, 5, and 6 give rise to an additional anion due to the hydrolysis of the ester group. The relative order of protonations to available sites is discussed. The ring-protonated species have shown the Ph, and indole rings to be coplanar in both the ground and first excited singlet states. A low-energy non-emissive twisted intramolecular charge transfer (TICT) state taking its origin in the dimethylamino moiety is suggested from INDO-S calculations to explain the strong fluorescence quenching of these ring-protonated species. Acidity constants for the various prototropic equilibria have been determined experimentally both in the ground and in the excited singlet states. Forster cycle calculations have been used to supplement the various equilibrium constants. Possible applications in organized assemblies are discussed. additionnel qui provient d'une hydrolyse de l'ester. On discute de I'ordre relatif des protonations des divers sites. On a dCmontrC que les espbces protonCes des cycles benzenique et indolique sont coplanaires tant dans 1'Ctat fondamental que dans le premier Ctat excitC. Sur la base de calculs INDO-S, on suggbre qu'un Ctat de transfert de charge intramolCculaire dCformC, de basse Cnergie, non radiatif et dont I'origine se trouverait dans la portion dimCthylamino peut expliquer la forte dksactivation de fluorescence de ces espbces protonkes sur le cycle. On a dCterminC experimentalement les constantes d'aciditt des divers Cquilibres prototropiques tant dans 1'Ctat fondamental que dans les Ctats excites. On a utilisC des calculs de cycles de Forster comme supplCments aux diverses constantes d'kquilibre. On discute de diverses applications possibles pour des systbmes organises.[Traduit par la rCdaction]

An absorption and fluorescence spectral study on the solubilization behaviour of 2-[@-amino)phenyl]-3,3dimethyl-5cyano-3H-indole (1) and 2-[@-dimethylamino)phenyl]-3,3-dimethyl-~yano-3H-indole (2) in sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) aqueous micelles has been carried out. Using spectral correlations with polarity parameters, bandwidths and photophysical parameters, the nature of the binding site of the molecules in micelles has been discussed. Both molecules occupy sites in SDS and CTAB that are less polar than water but accessible to it. The dimethylamino substituent helps in pushing the molecule toward the micellar core in both micelles. pH effects on the ring-nitrogen protonation (neutral-monocation equilibrium) and terminal nitrogen deprotonation (neutral-monoanion equilibrium) in SDS and CTAB, respectively, have also been discussed and found to be consistent with both the pseudophase ion-exchange (PIE) and electrostatic models.

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