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Issue 39, 2012
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The inhibition of iridium-promoted water oxidation catalysis (WOC) by cucurbit[n]urils

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Abstract

A series of iridacycles bearing π-bonded moieties of variable electron-withdrawing capabilities were tested for their ability to promote water oxidation catalysis (WOC) in the presence of high loading in a sacrificial oxidant, under conditions chosen for optimal dioxygen production. This report shows that none of these complexes performs differently than monometallic iridacycles and that the π-bonded moiety does not affect the overall rate of O2 production. Furthermore, it is shown that cucurbituril macrocycles significantly inhibit the production of dioxygen independently of the nature of the Cp*Ir(III)-based catalyst used to perform WOC. Theoretical first-principles based DFT-D3 investigations including a complete treatment of solvation with COSMO and COSMO-RS treatments supported by ITC analyses suggest that concealment of the catalyst by curcurbit[7]uril could occur by non-covalent interaction of the Cp*Ir moiety in the hydrophobic pocket of the cavitand. For other cavitands of smaller inner cavity diameter, inclusion may not be the main mode of inhibition. Assuming the intervention of the putative Ir(IV)–oxyl biradical of a Cp*IrIV(O)(H2O)2 species like suggested by many authors, inhibition of WOC by inclusion would probably result from unfavourable coulombic interactions between water and the inclusion complex.

Graphical abstract: The inhibition of iridium-promoted water oxidation catalysis (WOC) by cucurbit[n]urils

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Publication details

The article was received on 26 Jun 2012, accepted on 10 Aug 2012 and first published on 13 Aug 2012


Article type: Paper
DOI: 10.1039/C2DT31363D
Citation: Dalton Trans., 2012,41, 12233-12243
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    The inhibition of iridium-promoted water oxidation catalysis (WOC) by cucurbit[n]urils

    W. Iali, P. Petrović, M. Pfeffer, S. Grimme and J. Djukic, Dalton Trans., 2012, 41, 12233
    DOI: 10.1039/C2DT31363D

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