MIMICKING PRIMARY PROCESSES IN PHOTOSYNTHESIS-COVALENTLY-LINKED PORPHYRIN QUINONES

Porphyrin quinones (P-Qs), covalently linked via different aliphatic b ridges, have been synthesized and studies in their (porphyrin) cationi c and (semiquinone) anionic radical states by EPR, ENDOR and TRIPLE re sonance techniques. Electron transfer (ET) from the porphyrin donor to the quinone acceptor could be observed by time-resolved picosecond fl uorescence spectroscopy (singlet ET) and by time-resolved EPR spectros copy (triplet ET) in isotropic fluid solution and in anisotropic media (liquid crystals and reversed micelles). Steady-state in situ photoex citation of P-Qs in CTAB cationic reversed micelles yielded the corres ponding semiquinone radical anions. In TRITON X-100 reversed micelles both the radical cation of the porphyrin and the radical anion of the semiquinone could be detected, which occurred in complete emission. In covalently linked porphyrin flavins ET from the photoexcited porphyri n fragment to the flavin and, in addition, energy transfer from the ph otoexcited flavin to the porphyrin could be observed.