Photophysics of some substituted 3H-indole probe molecules and their charged species

Abstract

The spectroscopic and photophysical parameters of neutral and cationic species of the following molecules have been discussed: 2-phenyl-3,3-dimethyl-3H-indole (1). 2-[@-amino)phenyl]-3.3-dimethyl-3H-indole (2), 2-[QI-dimethylamino)phenyl]-3,3-dimethyl-3H-indole (3), 2-[@-amino)phenyl]-3,3-dimethyl-5-carboethoxy-3H-indole (4). 2-[@-methylamino)phenyl]-3,3-dimethyl-5-carboethoxy-3H-indole (5),2-[@-dimethylamino)phenyl]-3,3-dimethyl-5-carb0eth0xy-3H-ind0le (6). Solvatochromic shifts have been interpreted in terms of the nature of the substituent groups and the state of solute-solvent interactions and complexation. The theoretical radiative decay rate constant (kt;) along with the bandwidth of the absorption profile of the different species involved have been used to discuss the geometrical changes from one species to the other in the ground state. The mirror-image relationship between absorption and fluorescence spectra has proven to be a good tool to discuss any geometrical changes occuning in the excited state. A radiationless torsional mechanism takes place in the excited state relaxation of the various species. The protonation of the ring nitrogen atom generates a highly planar cationic species which retains its conformation in the relaxed excited state. The very effective quenching of the monocation fluorescence is interpreted by the formation of a non-emissive TICT state.MICHEL BELLE~TE, RANIIT S. SARPAL et GILLES DUROCHER'. Can. J. Chem. 72,2239Chem. 72, (1994. On discute des paramktres spectroscopiques et photophysiques des espkces neutres et cationiques suivantes: 2-phCnyl-3,3-dimtthyl-3H-indole (I), 2-[@-amino)phCnyl]-3,3-dimCthyl-3H-indole (2), 2-[(p-dimtthylamino)phtnyl]-3,3-dimtthyl-3H-indole (3), 2-[@-amino)phtnyl]-3,3-dimtthyl-5-carboCthoxy-3H-indole (4), 2-[@-mCthylamino)phCnyl]-3,3-dimethyl-5-carbotthoxy-3H-indole (5) et 2-[@-dimtthylamino)phCnyl]-3,3-dimCthyl-3H-indole (6).On interprkte les dCplacements solvatochromiques en fonction de la nature des substituants et de 1'Ctat des interactions et de la complexation solut6solvant. On a utilisC les constantes thCoriques de vitesse de la dCgCnCrescence radiative (kt;) de concert avec la largeur de bande du profile d'absorption des difftrentes espkces impliqutes pour discuter des changements de gtomCtrie se produisant d'une espkce B l'autre dans l'ttat fondamental. On a prouvC que la relation d'image dans un miroir entre les spectres d'absorption et de fluorescence est un bon outil pour discuter de tout changement gComCtrique se produisant dans 1'Ctat excitt. Un mecanisme de torsion sans radiation se produit dans la relaxation de 1'Ctat excitC des diverses espkces. La protonation de l'atome d'azote dy cycle gtnkre une espkce cationique trks plane qui retient sa conformation dans I'Ctat excitC relaxt. On interprkte la dtsactivation trks efficace de la fluorescence du monocation par la formation d'un Ctat TICT qui ne donne pas d'Cmission.[Traduit par la rCdaction]

3H-Indoles in Cetyltrimethylammonium Bromide (CTAB) Micelles and Water: Spectroscopy and Photophysics at Various Temperatures

“…tum yields and lifetimes of these 3H-indole probes, we have It is well known, for these molecules, that fluorescence quantum yields and lifetimes increase with the viscosity of nonpolar media and with the polarity of the nonaqueous environment (43)(44)(45)(46)(47). For the esters, in contrast, a strong decrease in both parameters was observed in water (49,50). A low energy, nonemissive, twisted intramolecular charge transfer (TICT) state was suggested to explain this fluorescence quenching in water for esters.…”

“…It is known for these molecules that the absorption energy decreases as one moves from nonpolar to polar aprotic solvents (44,45,49,50). But in contrast, the energy increases in water.…”

“…intramolecular charge transfer state (TICT) originating in the amino group (49)(50)(51)(52). By taking advantage of the envi-A wide variety of surfactant compounds can be dispersed ronment dependent spectral shifts of these molecules, we in aqueous solution to form organized assemblies, the struchave probed successfully the mean structural properties of tures of which depend upon the surfactant amphiphile and reverse micelles (47), aqueous micelles (53,54), and surthe experimental conditions used (1).…”

“…niques due to their simplicity, sensitivity at very low solute These molecules have already been studied in homogeneous concentration, and time domain (5-12). The peculiar make solvents (44)(45)(46) and aqueous solutions (49,50) such that up of micelles enables one to organize the reactants on a the main purpose here is to characterize the nature of the molecular level. By comparison of the data in micelles with interaction of these probes with CTAB using spectral and similar data in homogeneous solvents, one learns about the photophysical techniques.…”

Spectral and Photophysical Studies of the 1:3 (Guest/Host) Rotaxane-like Inclusion Complex Formed by a 3H-Indole and β-Cyclodextrin

“…[17][18][19][20][21][22][23][24][25][26][27] So far, we have probed successfully the mean structural properties of aqueous micelles, 23,24,26 reversed micelles, 25 and surfactant vesicles. 27 Very recently, we started a research program on the formation of inclusion complexes between cyclodextrins and some 3H-indoles, i.e., 2-(p-aminophenyl)-3,3-dimethyl-5-carboethoxy-3H-indole (2), 28 2-(p-methylaminophenyl)-3,3-dimethyl-5-carboethoxy-3H-indole (3), 29 2-(p-dimethylaminophenyl)-3,3-dimethyl-5-carboethoxy-3H-indole (4), 28 2-(p-aminophenyl)-3,3-dimethyl-5-cyano-3H-indole (5), 30,31 and 2-(p-dimethylaminophenyl)-3,3-dimethyl-5-cyano-3H-indole (6).…”