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Issue 8, 2011
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Structural variety in iridate oxides and hydroxides from hydrothermal synthesis

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Abstract

We report the results of an exploratory synthetic study of iridium-containing materials using hydrothermal methods from simple metal salts. Three alkali-earth iridium hydroxides are isolated as phase-pure samples and their structures examined by single-crystal or powder diffraction methods: each contains Ir(IV)-centred octahedra, isolated from each other and sharing bridging hydroxides or fluoride with alkali-earth (Ca, Sr or Ba) centres. One of these hydroxides, Ca2IrF(OH)6.OH, possesses a unique open structure, consisting of a positively-charged framework that has one-dimensional channels in which infinite chains of hydrogen-bonded hydroxide anions are encapsulated. The addition of hydrogen peroxide or sodium peroxide to otherwise identical hydrothermal reactions yields dense oxide materials in which iridium is found in an oxidation state between +4 and +5: the novel oxide Na0.8Sr2.2Ir3O10.1 has a KSbO3-type structure with an iridium oxidation state of +5, while the new pyrochlore (Na0.27Ca0.59)2Ir2O6·0.66H2O contains iridium with an average oxidation state close to +4.5. Our results illustrate the utility for hydrothermal synthesis in the discovery of novel complex structures that may be inaccessible using conventional high-temperature synthesis, with control of the metal oxidation state possible with judicious choice of reagents.

Graphical abstract: Structural variety in iridate oxides and hydroxides from hydrothermal synthesis

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Publication details

The article was received on 28 Mar 2011, accepted on 06 May 2011 and first published on 23 May 2011


Article type: Edge Article
DOI: 10.1039/C1SC00192B
Citation: Chem. Sci., 2011,2, 1573-1578
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    Structural variety in iridate oxides and hydroxides from hydrothermal synthesis

    K. Sardar, J. Fisher, D. Thompsett, M. R. Lees, G. J. Clarkson, J. Sloan, R. J. Kashtiban and R. I. Walton, Chem. Sci., 2011, 2, 1573
    DOI: 10.1039/C1SC00192B

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