PORPHYRIN AND PYROPHEOPHORBIDE PHOSPHORESCENCE IN SYNTHETIC MOLECULESTHAT MIMIC PHOTOSYNTHETIC TRIPLET ENERGY-TRANSFER

Phosphorescence emission and excitation spectra and triplet lifetimes at 77 K have been obtained for a carotenoid-porphyrin-pyropheophorbide triad model for the photosynthetic triplet energy transfer relay and seven porphyrin and pyropheophorbide model compounds including methyl pyropheophorbide-alpha. The results confirm that triplet energy from t he pyropheophorbide moiety of the triad is transferred to the caroteno id by a triplet energy relay involving endergonic transfer from the py ropheophorbide to the porphyrin, whose triplet is rapidly quenched by the carotenoid polyene.