Chiral hexamers of organically modified polyoxometalates via ionic complexation

Anderson-Evans type polyoxometalates (POMs) that are modified on double sides with anthracene groups through the covalent linking of β-amino acid enantiomers are synthesized. The modified Anderson-Evans POMs are successfully used for the construction of chiral hexamers where a chiral spacer is added through the ion complexation of a sodium ion. The novel chiral hexamer enantiomers maintain their structure stability in organic solvents and their structures and properties are characterized by a series of physicochemical measurements. The crystals are obtained by adding excess acetonitrile as the solvent. The crystal data analysis reveals that the chirality of the two hexamers with mirror symmetry is from three chiral axes perpendicular to each other, which are fixed by one Na-O subcluster at the central position and four Na-O subclusters distributed in a tetrahedral fashion. When an achiral linker is used to replace the chiral spacers, no hexamers are detected but a one-dimensional supramolecular polymer chain emerges instead.