Aggregation effects of hemotoporphyrin derivatives play an important role in the photodynamic therapy of cancer. We study a series of porphyrin derivatives Mn(3,4,5-0MeTPP)Cl, Mn(0-OC2H5TPP)Cl, (0-OC2H5TPP), Fe(0-OMeTPP)Cl, Mn(0-OMeTPP)Cl, TMP, P-ClTPP, TPP, THMPP, Fe(TPP)Cl, and Mn(THMPP)Cl shown in Fig. 1, which, in molecular structure, are similar to and simpler than hemotoporphyrin. The results of picosecond time-and-wavelength-resolved fluorescent spectroscopic study of their aggregation characteristics are presented. Samples are excited by a synchronously mode-locked Rh6G laser (pumped by an active mode-locked YAG laser with cavity damper). Fluorescence is measured with a spectrograph and synchroscan streak camera. Experiments show that fluorescence of Mn(3,4,5-0MeTPP)Cl, Mn(0-OC2H5TPP)Cl, (0-OC2H5TPP), Fe(0-OMeTPP)Cl, and Mn(0-OMeTPP)Cl in high concentration solutions are nonsingle exponential relaxation processes and their spectra change shapes with time after they are excited. Careful analysis supports that the fluorescence is a composition of three components with relaxation times of picosecond, subnanosecond, and picosecond, respectively. We owe these to the existence of monomer, dimer, and aggregation, which have different fluorescent spectra in both decay times and shapes.

© 1990 Optical Society of America

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