Role of Hydrogen-Bonding in the Formation of Polar Achiral and Nonpolar Chiral Vanadium Selenite Frameworks

A series of organically templated vanadium selenites have been prepared under mild hydrothermal conditions. Single crystals were grown from mixtures of VOSO4, SeO2, and either 1,4-dimethylpiperazine, 2,5-dimethylpiperazine, or 2-methylpiperazine in H2O. Each compound contains one-dimensional [VO(SeO3)(HSeO3)](n)(n-), 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 intra-secondary building unit and organic-inorganic hydrogen-bonding between compounds dictate the dimensionality of the resulting inorganic structures. [1,4-dimethylpiperazineH(2)] [VO(SeO3)(HSeO3)](2) contains one-dimensional [VO(SeO3)(HSeO3)](n)(n-) chains, while [2,5-dimethylpiperazineH(2)] [VO(SeO3)(HSeO3)](2)center dot 2H(2)O contains a three-dimensional [VO(SeO3)(HSeO3)](n)(n-) framework. The use of racemic 2-methylpiperazine also results in a compound containing a three-dimensional [VO(SeO3)(HSeO3)](n)(n-) framework, crystallizing in the noncentrosymmetric polar, achiral space group Pca2(1) (no. 29), while analogous reactions containing either (R)-2-methylpiperazine or (S)-2-methylpiperazine result in noncentrosymmetric, nonpolar chiral frameworks that crystallize in P2(1)2(1)2 (no. 18). The formation of these noncentrosymmetric framework materials is dictated by the structure, symmetry, and hydrogen-bonding properties of the [2-methylpiperazineH(2)](2+) cations.