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TRANSFER OF EXCITATION ENERGY BETWEEN PORPHYRIN CENTERS OF A COVALENTLY‐LINKED DIMER *
Author(s) -
Anton John A.,
Loach Paul A.
Publication year - 1978
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1978.tb07701.x
Subject(s) - porphyrin , chromophore , quantum yield , photochemistry , acceptor , chemistry , singlet state , free base , covalent bond , excited state , dimer , fluorescence , intramolecular force , monomer , stereochemistry , atomic physics , organic chemistry , polymer , physics , salt (chemistry) , quantum mechanics , condensed matter physics
— Three covalently‐linked porphyrin hybrid dimers were synthesized, each containing a metallotetraarylporphyrin [Zn(II), Cu(II), or Ni(II)], and a free base tetraarylporphyrin. Transfer of singlet excitation energy from the metalloporphyrin center to the free base porphyrin center was determined by measuring fluorescence properties. The Zn hybrid dimer displayed excellent intramolecular transfer of energy ( 85%) from the excited singlet state of the Zn(II) chromophore to the free base chromophore. No evidence for such transfer of the excited singlet state energy was found in the Ni(II) or Cu(II) analogues. From our experimental data, the fluorescence quantum yield of the Zn hybrid dimer was the same as for the free base monomer porphyrin (0.11; Seybold and Gouterman, 1969). Thus, the covalent attachment of another fluorescent porphyrin center effectively doubled the antenna size without decreasing the quantum yield even though the fluorescence quantum yield of the Zn(II) containing monomer was substantially less (0.03, according to Seybold and Gouterman, 1969) than that of the free base porphyrin. The donor‐acceptor distance and the rate constant for energy transfer were calculated using the Forster equation. Assuming random orientation, a donor‐acceptor distance of 15 Å was calculated with an associated rate constant (k ci ) for energy transfer of 1.9 ± 10 9 s –1 .