Photoionization processes of charged pyrene derivatives in reverse micelles. The effect of the interfacial charge

• The photopionization of pyrene sulofonic acid (PSA) and (4-(1-pyrenyl)butyl)trimethylammonium bromide (PBTMA) in reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and benzyl hexadecyl dimethylammonium chloride (BHDC) was investigated.
• A photoionization process is observed in BHDC for both probes, as is apparent by the presence of the radical cation of the pyrenyl group.
• The photoionization process was not detected in AOT.
• The results are interpreted by the different ability of AOT and BHDC to interact with the geminate radical–electron pair.

The laser flash photolysis studies of (4-(1-pyrenyl)butyl)trimethylammonium bromide (PBTMA) and 1-pyrene sulfonic acid (PSA) were carried out in BHDC and AOT reverse micellar solutions in benzene. At low laser intensities only the triplet state was observed as a transient species and the photophysical properties of the probes are very similar in both systems. Notable differences arise at high laser intensities. Under these conditions a photoionization process is observed in BHDC for both probes, as is apparent by the presence of the radical cation of the pyrenyl group. Hydrated electrons are not observed at times longer than 100 ns. On the other hand the photoionization process is not detected in AOT. However, a slight photoionization may be induced in AOT by the presence of benzyl alcohol. These results are interpreted by the different ability of AOT and BHDC to interact with the geminate radical–electron pair.