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Role of the Special Pair in the Charge‐Separating Event in Photosynthesis
Author(s) -
Ozeki Hidekane,
Nomoto Akihiro,
Ogawa Kazuya,
Kobuke Yoshiaki,
Murakami Masataka,
Hosoda Kou,
Ohtani Masana,
Nakashima Satoru,
Miyasaka Hiroshi,
Okada Tadashi
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400624
Subject(s) - dimer , delocalized electron , photochemistry , chemistry , monomer , acceptor , porphyrin , ultrafast laser spectroscopy , radical ion , spectroscopy , physics , organic chemistry , condensed matter physics , polymer , quantum mechanics , ion
Abstract We synthesized special‐pair/electron‐acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl‐substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole π system of the dimer. Time‐resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped cofacial dimer relative to that of the monomeric system demonstrates the significance of the special‐pair arrangement for efficient charge separation in photosynthesis.