Face-to-face stacking of caffeinium and [PMVI12O40]3− ions: A synthon for crystal engineering with purine bases

Abstract

Ionic polyoxometales (Hcaf)3[PM12O40]·6H2O [M = Mo, W; caf = caffeine] exhibit unusual supramolecular structure dominated by multiple anion-π interactions, which occur at both axial sides of the caffeinium cations. These cations, when stacked to every of six square faces of POM cuboctahedra, afford supramolecular boxes and the resulting non-covalent cubic framework (α-Po topology) is generated by face-sharing of the boxes.