INVESTIGATION OF ENERGY-TRANSFER AND CHARGE-TRANSFER PROCESSES USING SELF-ORGANIZED PORPHYRIN AGGREGATES

Self-assembled triads and pentads are formed from Zn-porphyrin or Zn-c hlorin dimers and pyridyl-substituted free base of porphyrins, chlorin s or tetrahydroporphyrins. A two-point co-ordination of the central Zn ions in the dimer with the nitrogen atoms of the pyridyl substituents of the free bases is essential for the complex formation. The complex ation process has an equilibrium constant of the order of 10(7) M(-1) at room temperature. An activation energy of the thermal dissociation of the complexes of 0.8 eV is found, which does not differ very much f or different kinds of aggregates. Competing energy and charge transfer processes taking place in the aggregates have been identified by temp erature dependent steady slate fluorescence measurements.