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Direct Copper(III) Formation from O2 and Copper(I) with Histamine Ligation
journal contribution
posted on 2016-07-28, 12:48 authored by J. Brannon Gary, Cooper Citek, Timothy
A. Brown, Richard N. Zare, Erik C. Wasinger, T. Daniel P. StackHistamine chelation of copper(I)
by a terminal histidine residue
in copper hydroxylating enzymes activates dioxygen to form unknown
oxidants, generally assumed as copper(II) species. The direct formation
of copper(III)-containing products from the oxygenation of histamine-ligated
copper(I) complexes is demonstrated here, indicating that copper(III)
is a viable oxidation state in such products from both kinetic and
thermodynamic perspectives. At low temperatures, both trinuclear Cu(II)2Cu(III)O2 and dinuclear Cu(III)2O2 predominate, with the distribution dependent on the histamine
ligand structure and oxygenation conditions. Kinetics studies suggest
the bifurcation point to these two products is an unobserved peroxide-level
dimer intermediate. The hydrogen atom reactivity difference between
the trinuclear and binuclear complexes at parity of histamine ligand
is striking. This behavior is best attributed to the accessibility
of the bridging oxide ligands to exogenous substrates rather than
a difference in oxidizing abilities of the clusters.
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copper hydroxylating enzymes activates dioxygenexogenous substratesoxygenation conditionsoxidation stateoxidizing abilitieshistamine ligandO 2oxide ligandsHistamine Ligation Histamine chelationterminal histidine residuebifurcation pointKinetics studieshydrogen atom reactivity differencehistamine ligand structureCu
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