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Intermolecular and intracomplex photoinduced electron transfer from planar and nonplanar metalloporphyrins to p-quinones

Title
Intermolecular and intracomplex photoinduced electron transfer from planar and nonplanar metalloporphyrins to p-quinones
Authors
Kanematsu M.Naumov P.Kojima T.Fukuzumi S.
Ewha Authors
Shunichi Fukuzumi
SCOPUS Author ID
Shunichi Fukuzumiscopus
Issue Date
2011
Journal Title
Chemistry - A European Journal
ISSN
0947-6539JCR Link
Citation
vol. 17, no. 44, pp. 12372 - 12384
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
The rate constants of intermolecular photoinduced electron transfer from triplet excited states of metalloporphyrins to a series of p-benzoquinone derivatives in benzonitrile were determined to examine the effects of the driving force, the metal, and the conformational distortion of the porphyrin ring on the reorganization energies (λ) of electron transfer by laser flash photolysis. The λ values were evaluated from the determined rate constants on the basis of the Marcus theory of electron transfer. The λ values of planar metalloporphyrins, [Al(TPP)(PhCOO)] and [Zn(TPP)] (TPP 2-=tetraphenylporphyrin dianion), are approximately the same, but they are 0.27 eV smaller than those of the corresponding nonplanar (saddle-distorted) metalloporphyrins [Al(DPP)(PhCOO)] and [Zn(DPP)] (DPP 2-=dodecaphenylporphyrin dianion) when they are compared for the same driving force of photoinduced electron transfer. The axial ligand PhCOO - of [Al(TPP)] + and [Al(DPP)] + was replaced by anthraquinone-2-carboxylate (AqCOO -) to afford the electron donor-acceptor complexes [Al(TPP)(AqCOO)] and [Al(DPP)(AqCOO)], respectively. The X-ray crystal structure of [Al(TPP)(AqCOO)] revealed strong coordination of AqCOO - to the Al 3+ ion of [Al(TPP)] + and the existence of π-π interactions between AqCOO - and the porphyrin ring. In the case of the saddle-distorted [Al(DPP)(AqCOO)], however, the AqCOO - moiety is nearly perpendicular to the porphyrin ring. The photodynamics of intracomplex photoinduced electron transfer from the singlet excited state of [Al(TPP)] + and [Al(DPP)] + to the AqCOO - moiety were also examined in comparison with the intermolecular photoinduced electron-transfer reactions, and the determined rate constants were evaluated in light of the Marcus theory of electron transfer to reveal that the electron transfer is adiabatic in each case. Photodynamics: The intermolecular, photoinduced electron-transfer properties of planar and nonplanar Al III porphyrins as electron donors were revealed by comparison with Zn II porphyrins. The photodynamics of intracomplex, photoinduced electron transfer from planar and nonplanar Al III porphyrins to the anthraquinone moieties (see figure) were examined in comparison with the intermolecular, photoinduced electron-transfer reactions. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
DOI
10.1002/chem.201100493
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자연과학대학 > 화학·나노과학전공 > Journal papers
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