C O M M U N I C A T I O N S
suggest that even subtle charge modulation at the heme active site
of P450 to accomplish a similar tuning of state-crossing energies
or lower stability of the porphyrin π-radical cation could result in
high reactivity of a cytochrome P450 compound I.
Acknowledgment. Support of this research by the National
Institutes of Health (R37-GM36298) and the National Science
Foundation (CHE 0316301) is gratefully acknowledged.
Supporting Information Available: Experimental details and NMR
data (Figure S1). This material is available free of charge via the Internet
at http://pubs.acs.org.
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6
-1
oxidation by 1 at pH 4.7, 14.5 °C, yielding k
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The interesting question is why synthetic OFe -porphyrin
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manifolds, stabilization of the porphyrin HOMO, and the unique
2
5
centrosymmetric trans-dioxo ligand arrangement. Clearly, the
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Fe -4-TMPyP. Further, efficient transmission of the electron deficit
to the metal core is assured by the large orbital coefficients on the
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(
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(
III
a
of the axial water in diaquaFe -4-TMPyP is only
1
III
26
5
1
(
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(
(
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(
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2,28
and iron.
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of an unsubstituted oxoFe -porphyrin radical cation, with the iron
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1
3310–13320.
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2
9
state structures. We suggest that the high kinetic reactivity
observed here experimentally for 1 may result from both a low-
lying a2u porphyrin HOMO and facilitated spin-state crossing
phenomena in the course of the reaction. More generally, the results
(
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