PHOTOPHYSICAL CHARACTERIZATION OF SULFONATED ALUMINUM PHTHALOCYANINESIN A CATIONIC REVERSED MICELLAR SYSTEM

The photophysics of sulfonated aluminum phthalocyanines, AIPcS(n) (n = 0, 1, 2, 3, or 4), in cationic reversed micelles of benzyldimethyl-n- hexadecylammonium chloride (BHDC) have been investigated. Absorption a nd steady-state fluorescence emission spectroscopy indicate that only the di- and trisulfonated derivatives are essentially monomeric. Conse quently, the triplet-state properties of only these nonaggregated phth alocyanines were investigated. Both derivatives exhibited enhanced int ersystem crossing in this medium compared to homogeneous environments, yet the singlet oxygen quantum yields were found to be comparable to those obtained in homogeneous solutions. Time-resolved fluorescence em ission studies yielded decays which were best fitted by a decay time d istribution analysis rather than the more commonly used sum of exponen tials model. The distributions were seen to broaden with increasing wa ter concentration. The distribution of AIPcS(n) in the reversed micell es, which appears to be strongly influenced by the extent of sulfonati on and the environment within the reversed micelle, is discussed.