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Enhanced Intersystem Crossing in Donor/Acceptor Systems Based on Zinc/Iron or Free-Base/Iron Porphyrins

Kilså, Kristine (författare)
Chalmers tekniska högskola,Chalmers University of Technology
Kajanus, Johan (författare)
Chalmers tekniska högskola,Chalmers University of Technology
Larsson, Sven, 1941 (författare)
Chalmers tekniska högskola,Chalmers University of Technology
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Macpherson, Alisdair N (författare)
Umeå universitet,Kemiska institutionen
Mårtensson, Jerker, 1965 (författare)
Chalmers tekniska högskola,Chalmers University of Technology
Albinsson, Bo, 1963 (författare)
Chalmers tekniska högskola,Chalmers University of Technology
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 (creator_code:org_t)
2001
2001
Engelska.
Ingår i: Chemistry, A European Journal. - 1521-3765 .- 0947-6539. ; 7:10, s. 2122-33
  • Tidskriftsartikel (refereegranskat)
Abstract Ämnesord
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  • The deactivation pathways of the singlet excited state of a series of zinc or free-base donor porphyrins covalently linked by a bridge to a paramagnetic iron(iii) chloride porphyrin acceptor have been studied. These donor-bridge-acceptor systems all share a similar geometry (25 Å donor-acceptor center-to-center distance), but the bridges vary in electronic structure. In previously reported investigations of zinc/iron porphyrin systems, the fluorescence quenching of the donor has predominantly been assigned to electron transfer. However, for the porphyrin systems studied in this paper, we show that the dominant deactivation channels are enhanced intersystem crossing and singlet energy transfer. In both series, the intersystem crossing rate (S1T1) of the donor moiety is almost doubled in the presence of a paramagnetic high-spin metal-porphyrin acceptor. The significant spectral overlap of the donor fluorescence and acceptor absorption in both series allows for efficient singlet energy transfer (Förster mechanism). Furthermore, the bridging chromophores mediate energy transfer and the enhancement is inversely dependent upon the energy gap between the donor and bridge excited states. Although Marcus theory predicts thermodynamically favorable electron transfer to occur in the systems investigated, the quenching rate constants were found to be independent of solvent polarity, and no charge-separated state could be detected, indicating very small electronic coupling for electron transfer.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2111/2001/f2779_s.pdf or from the author. 1H NMR spectra of FeP, FeP-OB, FeP-BB, FeP-NB, FeP-AB, ZnP-OB-FeP, ZnP-BB-FeP, ZnP-NB-FeP, and ZnP-AB-FeP.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)
NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

donor-acceptor systems
electron transfer
intersystem crossing
mediated energy transfer
porphyrinoids

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