Chemistry Reference
In-Depth Information
PD2
PD1
PD6
PD7
PD3
PD4
PD8
PD9
PD5
PD10
PD11
SCHEME 9.7
The geometries of Dp
2
+
, Dp
3
+
, and Dp
4
+
used in the g-tensor calculations (Dp is the
p
-
dimethylenebenzene molecule). Face-to-face coni gurations PD1, PD2, and PD3 are shown for clarity. (From
Petrenko, A.,
Chem. Phys. Lett
., 406, 327, 2005. With permission.)
9.18 CONCLUSIONS
Carotenoid radical intermediates generated electrochemically, chemically, and photochemically
in solutions, on oxide surfaces, and in mesoporous materials have been studied by a variety of
advanced EPR techniques such as pulsed EPR, ESEEM, ENDOR, HYSCORE, and a multifre-
quency high-i eld EPR combined with EPR spin trapping and DFT calculations. EPR spectroscopy
is a powerful tool to characterize carotenoid radicals: to resolve
g
-anisotropy (HF-EPR), anisotropic
coupling constants due to
-protons (CW, pulsed ENDOR, HYSCORE), to determine distances
between carotenoid radical and electron acceptor site (ESEEM, relaxation enhancement).
α
ACKNOWLEDGMENTS
We thank the U.S. Department of Energy, Grant DE-FG02-86ER13465 and the National Science
Foundation, Grant CHE-0079498 for support.
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crystals of
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