Oxygen Activation with Transition-Metal Complexes in Aqueous Solution

Abstract

Coordination to transition-metal complexes changes both the thermodynamics and kinetics of oxygen reduction. Some of the intermediates (superoxo, hydroperoxo, and oxo species) are close analogues of organic oxygen-centered radicals and peroxides (ROO(*), ROOH, and RO(*)). Metal-based intermediates are typically less reactive, but more persistent, than organic radicals, which makes the two types of intermediates similarly effective in their reactions with various substrates. The self-exchange rate constant for hydrogen-atom transfer for the couples Cr(aq)OO(2+)/Cr(aq)OOH(2+) and L(1)(H(2)O)RhOO(2+)/L(1)(H(2)O)RhOOH(2+) was estimated to be 10(1+/-1) M(-1) s(-1). The use of this value in the simplified Marcus equation for the Cr(aq)O(2+)/Cr(aq)OOH(2+) cross reaction provided an upper limit k(CrO,CrOH) <or= 10((-2+/-1)) M(-1) s(-1) for Cr(aq)O(2+)/Cr(aq)OH(2+) self-exchange. Even though superoxo complexes react very slowly in bimolecular self-reactions, extremely fast cross reactions with organic counterparts, i.e., acylperoxyl radicals, have been observed. Many of the intermediates generated by the interaction of O(2) with reduced metal complexes can also be accessed by alternative routes, both thermal and photochemical.

Low temperature oxidation of linseed oil: a review

“…The dioxygen activation is indicated by the O-O bond lengthening and Co-O distance shortening (Boca 1983). Transition metal complexes fulfil important roles in activating the molecular oxygen through the coordination and partial reduction of oxygen (Bakac 2010). Smeets et al investigated the coordination and activation of oxygen employing transition metal ions in zeolites (Smeets et al 2010).…”

Enhanced Catalytic Four-Electron Dioxygen (O2) and Two-Electron Hydrogen Peroxide (H2O2) Reduction with a Copper(II) Complex Possessing a Pendant Ligand Pivalamido Group

“…1–4 Extensive efforts have been devoted to develop synthetic Fe a3 /Cu B analogs, because the four-electron four-proton reduction of O 2 has attracted much attention from the viewpoint not only of great biological interest, 5–11 but also of technological significance such as in fuel cells. 12–15 Multicopper oxidases such as laccase (possessing four copper ions centers per functional unit) can also catalyzed the four-electron four-proton reduction of O 2 , (the “ORR”) at potentials approaching 1.2 V (vs RHE).…”

Oxidative Dissolution of Silver Nanoparticles by Dioxygen: A Kinetic and Mechanistic Study

“…[1] Likewise, oxidation of metal nanoparticles by O 2 is important to the advancement of nanotechnology because oxidative dissolution of metal nanoparticles to corresponding metal ions is a powerful tool for the synthesis of well-defined nanostructured materials, [2][3][4] and is related to their biological activities. [1] Likewise, oxidation of metal nanoparticles by O 2 is important to the advancement of nanotechnology because oxidative dissolution of metal nanoparticles to corresponding metal ions is a powerful tool for the synthesis of well-defined nanostructured materials, [2][3][4] and is related to their biological activities.…”

“…Oxidation of metal complexes by O 2 is a crucial reaction in many biological systems and chemical processes. [1] Likewise, oxidation of metal nanoparticles by O 2 is important to the advancement of nanotechnology because oxidative dissolution of metal nanoparticles to corresponding metal ions is a powerful tool for the synthesis of well-defined nanostructured materials, [2][3][4] and is related to their biological activities. [5][6][7][8] A noted example is the controlled release of biologically active Ag + ion from AgNPs which is governed by oxidative dissolution of AgNPs.…”