pH-Tuned self-assembly of organic–inorganic hybrids based on different vanadate chains, Zn(ii) ions and flexible ligands: crystallizing in polar and centrosymmetric space group

Abstract

Three organic–inorganic hybrid compounds have been designed and synthesized based on different vanadate chains, Zn(II) ions and flexible ligands at different pH values under hydrothermal conditions, namely, [Zn₂(bbi)₂(V₃O₉)(OH)]·H₂O (1), [Zn₂(bbi)₂(V₄O₁₂)] (2), and [Zn(bbi)(V₂O₆)] (3), where bbi is 1,1′-(1,4-butanediyl)bis(imidazole). In 1, helical chains [(V₃O₉)³⁻]_∞ were connected by [Zn₂(OH)]³⁺ dimers giving rise to a 2D chiral layer which was further bridged via bbi ligands to construct a 3D POM-based chiral framework. There are two opposite helical chains [(V₄O₁₂)⁴⁻]_∞ in 2. The [(V₄O₁₂)⁴⁻]_∞ chains with the same chirality were connected each other by Zn2 cations to generate a 2D chiral layer, respectively. The adjacent chiral layers were linked by Zn1 ions to generate a 3D non-centrosymmetric framework with large channel encased by bbi. Similarly, the [(V₂O₆)²⁻]_∞ chains with the same chirality in 3 were connected by zinc atoms to form a 2D chiral layer which was further linked through bbi to generate a 3D centrosymmetric network. Compounds 2 and 3 are supramolecular isomers. With adjusting the pH value of reaction mixture, we have achieved three new hybrids crystallized from chiral, non-centrosymmetric to centrosymmetric space group.