Sardar, Kripasindhu, Fisher, Janet M., Thompsett, David, Lees, Martin R., Clarkson, Guy J., Sloan, Jeremy, Kashtiban, Reza J. and Walton, Richard I.. (2011) Structural variety in iridate oxides and hydroxides from hydrothermal synthesis. Chemical Science, Vol.2 (No.8). pp. 1573-1578. ISSN 2041-6520

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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, Ca(2)IrF(OH)(6)center dot 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 Na(0.8)Sr(2.2)Ir(3)O(10.1) has a KSbO(3)-type structure with an iridium oxidation state of +5, while the new pyrochlore (Na(0.27)Ca(0.59))(2)Ir(2)O(6)center dot 0.66H(2)O 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.

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Item Type:	Journal Article
Subjects:	Q Science > QC Physics Q Science > QD Chemistry
Divisions:	Faculty of Science > Chemistry Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Iridium -- Magnetic properties, Crystallization, Crystals -- Structure, X-ray crystallography, X-ray absorption near edge structure, High temperature chemistry
Journal or Publication Title:	Chemical Science
Publisher:	Royal Society of Chemistry
ISSN:	2041-6520
Date:	2011
Volume:	Vol.2
Number:	No.8
Page Range:	pp. 1573-1578
Identification Number:	10.1039/c1sc00192b
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC), European Regional Development Fund (ERDF)
Grant number:	EP/F012721/1 (EPSRC)
URI:	http://wrap.warwick.ac.uk/id/eprint/38706

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