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Synthesis and Structural Characterization of ... - Jacobs University

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Chapter 1<br />

Introduction<br />

Removal <strong>of</strong> two adjacent octahedra from α- <strong>and</strong> β-[XW 12 O 40 ] n− isomers has not been<br />

observed, but only for the γ isomer, the [XM 10 O 36 ] n− , see Figure 1.8. The plenary polyanions<br />

are stabilized under very acidic conditions (pH 0-2), monolacunary species are found at<br />

slightly acidic pH (4-6), <strong>and</strong> trilacunary ones are stable at pH (8-10).<br />

β 1 -[XW 11 O 39 ] n−<br />

β 2 -[XW 11 O 39 ] n−<br />

β 3 -[XW 11 O 39 ] n−<br />

- 1<br />

β-[XW 12 O 40 ] n−<br />

A-β-[XW 9 O 34 ] n−<br />

- 3<br />

B-β-[XW 9 O 34 ] n−<br />

Figure 1.7 Lacunary species derived from the β-Keggin structure. Red <strong>and</strong> yellow octahedra:<br />

MO 6 , green sphere: X heteroatom, red sphere: oxygen.<br />

14

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