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-dimethylpiperazineH2][VO(SeO3)(HSeO3)]2 contains one-dimensional [VO(SeO3)(HSeO3)]n n‑ chains, while [2,5-dimethylpiperazineH2][VO(SeO3)(HSeO3)]2·2H2O 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 Pca21 (no. 29), while analogous reactions containing either (R)-2-methylpiperazine or (S)-2-methylpiperazine result in noncentrosymmetric, nonpolar chiral frameworks that crystallize in P21212 (no. 18). The formation of these noncentrosymmetric framework materials is dictated by the structure, symmetry, and hydrogen-bonding properties of the [2-methylpiperazineH2]2+ cations.