Oxidation of exogenous substrates by the O2-evolving center of photosystem II and related catalytic air oxidation of secondary alcohols via a tetranuclear manganese(IV) complex.

Warren F. Beck, Jonathan Sears, Gary W Brudvig, Robert J. Kulawiec, Robert H. Crabtree

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Abstract

The O2-evolving center of Photosystem II (PSII) contains atetranuclear Mn complex that acts as the catalyst for photosynthetic H2O oxidation. The catalytic cycle for H2O oxidation is thought to involve the light-driven generation of a very strongly oxidizing state of the Mn complex prior to the formation of the OO bond. However, the Mn complex also exhibits oxidation chemistry in its lower oxidation states. Exogenous ligands, such as primary amines and hydroxylamines, have been shown previously to interact with the O2-evolving center in the dark S1 oxidation state by coordinating to a Cl--binding site near the Mn complex. In this paper, we present evidence that primary and secondary amines irreversibly inactivate the Mn complex in the S1 state by a reductive mechanism, leading to the liberation of Mn(II) ions and a concomitant loss of O2-evolution activity. Hence, the Mn complex in the O2-evolving center acts as a strong oxidant even in the dark-stable S1 state. The synthetic tetranuclear Mn(IV) complex [(TACN)4Mn4O6]Br4, which has been suggested as a model for the Mn complex in the O2-evolving center, is a strong oxidant as well. We find that it catalyzes the air oxidation of secondary alcohols to ketones and triphenylphosphine to triphenylphosphine oxide.

Original languageEnglish
Pages (from-to)4903-4911
Number of pages9
JournalTetrahedron
Volume45
Issue number15
DOIs
Publication statusPublished - 1989

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Photosystem II Protein Complex
Manganese
Oxidants
Amines
Hydroxylamines
Air
Alcohols
Oxidation
Substrates
Ketones
Binding Sites
Ions
Ligands
Light
Catalysts
triphenylphosphine
triphenylphosphine oxide

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Drug Discovery

Cite this

Oxidation of exogenous substrates by the O2-evolving center of photosystem II and related catalytic air oxidation of secondary alcohols via a tetranuclear manganese(IV) complex. / Beck, Warren F.; Sears, Jonathan; Brudvig, Gary W; Kulawiec, Robert J.; Crabtree, Robert H.

In: Tetrahedron, Vol. 45, No. 15, 1989, p. 4903-4911.

Research output: Contribution to journalArticle

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abstract = "The O2-evolving center of Photosystem II (PSII) contains atetranuclear Mn complex that acts as the catalyst for photosynthetic H2O oxidation. The catalytic cycle for H2O oxidation is thought to involve the light-driven generation of a very strongly oxidizing state of the Mn complex prior to the formation of the OO bond. However, the Mn complex also exhibits oxidation chemistry in its lower oxidation states. Exogenous ligands, such as primary amines and hydroxylamines, have been shown previously to interact with the O2-evolving center in the dark S1 oxidation state by coordinating to a Cl--binding site near the Mn complex. In this paper, we present evidence that primary and secondary amines irreversibly inactivate the Mn complex in the S1 state by a reductive mechanism, leading to the liberation of Mn(II) ions and a concomitant loss of O2-evolution activity. Hence, the Mn complex in the O2-evolving center acts as a strong oxidant even in the dark-stable S1 state. The synthetic tetranuclear Mn(IV) complex [(TACN)4Mn4O6]Br4, which has been suggested as a model for the Mn complex in the O2-evolving center, is a strong oxidant as well. We find that it catalyzes the air oxidation of secondary alcohols to ketones and triphenylphosphine to triphenylphosphine oxide.",
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