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Cation Radicals of Covalently Linked Porphyrin Dimers and their Monomeric Constituents: An ESR and ENDOR Study
Author(s) -
Huber Martina,
Galili Tamar,
Möbius Klaus,
Leva Haim
Publication year - 1989
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198900010
Subject(s) - chemistry , delocalized electron , porphyrin , dimer , unpaired electron , radical , monomer , photochemistry , intramolecular force , covalent bond , electron paramagnetic resonance , crystallography , hyperfine structure , stereochemistry , nuclear magnetic resonance , organic chemistry , physics , quantum mechanics , polymer
The spin density distributions in the cation radicals of various covalently linked porphyrin dimers have been studied by liquid phase ESR and ENDOR methods to find out whether these systems show intramolecular electron delocalization. Such a delocalization is known to occur in the bacteriochlorophyll dimer (“special pair”) in the photosynthetic reaction center. The dimers that were studied in this work were derived from zinc meso tetratolylporphyrin (ZnTTP) and linked at the ortho or para positions of one phenyl ring with varying bridge lengths. 1 H and I4 N hyperfine coupling constants could be measured for the dimer cation radicals and compared with those of monomeric ZnTTP as well as ZnTTP derivatives that carry alkoxy or hydroxy substituents to mimic the bridges of the dimers. By comparing the hyperfine data of the monomer and dimer cation radicals it is concluded that in the present dimers the unpaired electron is localized on one porphyrin unit.