Role of Hydrogen-Bonding
in the Formation of Polar
Achiral and Nonpolar Chiral Vanadium Selenite Frameworks
- Publication date
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Abstract
A series of organically templated vanadium selenites
have been
prepared under mild hydrothermal conditions. Single crystals were
grown from mixtures of VOSO<sub>4</sub>, SeO<sub>2</sub>, and either
1,4-dimethylpiperazine, 2,5-dimethylpiperazine, or 2-methylpiperazine
in H<sub>2</sub>O. Each compound contains one-dimensional [VO(SeO<sub>3</sub>)(HSeO<sub>3</sub>)]<sub>n</sub><sup>n‑</sup> secondary
building units, which connect to form three-dimensional frameworks
in the presence of 2,5-dimethylpiperazine or 2-methylpiperazine. Differences
in composition and both <i>intra</i>-secondary building
unit and organic–inorganic hydrogen-bonding between compounds
dictate the dimensionality of the resulting inorganic structures.
[1,4-dimethylpiperazineH<sub>2</sub>][VO(SeO<sub>3</sub>)(HSeO<sub>3</sub>)]<sub>2</sub> contains one-dimensional [VO(SeO<sub>3</sub>)(HSeO<sub>3</sub>)]<sub>n</sub><sup>n‑</sup> chains, while
[2,5-dimethylpiperazineH<sub>2</sub>][VO(SeO<sub>3</sub>)(HSeO<sub>3</sub>)]<sub>2</sub>·2H<sub>2</sub>O contains a three-dimensional
[VO(SeO<sub>3</sub>)(HSeO<sub>3</sub>)]<sub>n</sub><sup>n‑</sup> framework. The use of racemic 2-methylpiperazine also results in
a compound containing a three-dimensional [VO(SeO<sub>3</sub>)(HSeO<sub>3</sub>)]<sub>n</sub><sup>n‑</sup> framework, crystallizing
in the noncentrosymmetric polar, achiral space group <i>Pca</i>2<sub>1</sub> (no. 29), while analogous reactions containing either
(<i>R</i>)-2-methylpiperazine or (<i>S</i>)-2-methylpiperazine
result in noncentrosymmetric, nonpolar chiral frameworks that crystallize
in <i>P</i>2<sub>1</sub>2<sub>1</sub>2 (no. 18). The formation
of these noncentrosymmetric framework materials is dictated by the
structure, symmetry, and hydrogen-bonding properties of the [2-methylpiperazineH<sub>2</sub>]<sup>2+</sup> cations
