The Processes of Crown-Substituted Magnesium Phthalocyaninate Dissolution in Water in the Presence of Alkyltrimethylammonium Bromides

Electronic absorption and luminescence spectroscopies have been employed to analyze the processes of octa-crown-substituted magnesium phthalocyaninate (Mgcr8Pc) dissolution in water in the presence of dodecyl-, tetradecyl-, and hexadecyltrimethylammonium bromides. In the premicellar region of surfactant concentrations, surfactant-induced aggregation of Mgcr8Pc prevails. Above the critical micelle concentration of the surfactants, Mgcr8Pc is completely disaggregated to monomers. At the same time, an increase in the alkyl chain length in a surfactant molecule enhances the tendency to its monomerization, as is evident from the results of measuring the electronic absorption and fluorescence spectra, as well as the fluorescence decay kinetics data. A rise in the fluorescence lifetime of Mgcr8Pc with compacting micelles suggests a decline in the degree of their hydration, which leads to a decrease in the polarity of Mgcr8Pc microenvironment. Mgcr8Pc exhibits intense fluorescence in hexadecyltrimethylammonium bromide solutions both at room temperature and after rapid freezing to 77 K, thus confirming that the disaggregated state of Mgcr8Pc molecules remains preserved in micelles even at this low temperature. The results obtained indicate that Mgcr8Pc dissolved in solutions of alkyltrimethylammonium bromides can be used in photodynamic therapy of tumors in combination with cryolysis procedures.