PHOTOPHYSICAL STUDIES OF INDOLE ALKANOIC ACIDS and TRYPTAMINE IN REVERSE MICELLES OF SODIUM DIOCTYL SULFOSUCCINATE

Abstract

Abstract— The fluorescence spectra and emission lifetimes of several 3‐alkanoic indoles of different chain length and tryptamine (TA) were studied in sodium dioctyl sulfosuccinate (AOT)/heptane reverse micelles over a wide range of water/AOT ratio (R ‐ 5 to 44). Fluorescence quenching experiments were done using carbon tetrachloride and acrylamide as quenchers. Experiments with TA were carried out using water at pH 3 in order to assure its protonation. Under these conditions, the results indicate that the indole moiety of TA remains at the micellar interface over all the range considered. Furthermore, the results can be interpreted assuming for the TA population a single microenvironment whose properties remain almost invariant when R increases from 11 to 44. The studies employing the 3‐alkanoic indoles were carried out at pH 10. Under these conditions, the anions are progressively displaced to the water pool when the R value increases. This displacement is determined by the length of the side alkyl chain of the 3‐indole derivatives. For these compounds, the quenching experiments indicate that, even at low R values, the excited indole moieties are distributed among different microenvironments.

Deactivation of Pyrene Derivatives by Nitroxides in AOT Reverse Micelles. Dependence of Quenching Efficiency on the Probe and Quencher Location in the Microaggregates

“…At low R values, the difference with the data obtained for the cationic probe indicates that, in spite of the fact that both charged probes are associated to the interface, their relative location must be widely different, with a deeper location of the polyanion. Similar results have been previously reported regarding the location of ruthenium complexes in AOT micelles, pyrene derivatives, indolic derivatives, and Cu 2+ and I - ions 13 in AOT micelles, indicating that, even in the absence of a water pool, the average locations of anionic and cationic probes are widely different. This difference, that appears to be almost independent on the considered system and determined by the charge of the surfactant and the probe, has been explained in terms of an inner location of the co-ions …”

“…Reverse micelles comprise at least three well-differentiated regions, the dispersium solvent, the interface, and the water pool, allowing the location of solutes in widely different environments. − Fluorescence quenching studies of probes associated to different locations can provide information regarding the distribution of the donor and the quencher − and/or the rate of access of the quencher to the different subregions of the microheterogeneous solution . Most of these works have been performed comprising donors and quenchers totally incorporated to the micellar pseudophase, and few studies have been carried out employing families of quenchers of different hydrophobicity and donors located in different environments. , This type of study can provide information regarding the distribution and mobility of the quencher and/or the donor as a function of their structure and the properties of the micelles, determined by the water/surfactant ratio.…”

Influence of Polarity and Viscosity of the Micellar Interface on the Fluorescence Quenching of Pyrenic Compounds by Indole Derivatives in AOT Reverse Micelles Solutions

“…The effect of the water content, measured as R ϭ [water]/[AOT], on the quenching rate constants was investigated. The quenchers include compounds that reside mainly in the organic phase, N-methyl indoles, molecules that are partitioned between the organic phase and the interface, indole itself, and the biological relevant indole derivatives, tryptophan and tryptamine, that are located in the interface (5,7,11). The probes are the pyrene derivatives 1-pyrenesulfonic acid (PSA), 1-pyrenemethyltrimethylammonium iodide (PMTMA) and 1-pyrenebutyltrimethylammonium bromide (PBTMA).…”

Nature of the Water Structure inside the Pools of Reverse Micelles Sensed by Laser-Induced Optoacoustic Spectroscopy

“…An additional interest in studying weak interactions such as hydrogen bonds inside reverse micelles resides in the fact that the highly structured water molecules in the reverse micelles can be thought of as primitive models of the water molecules in biological systems. ,,, …”