Encapsulation of a double-helical water–nitrate chain inside unique double helical chiral channels formed from Keggin POM and hexaquo-cobalt(II) units

Abstract

A new inorganic–organic hybrid chiral molecule [Co(H2O)6][C5H6N]H4[CoW12O40]NO3·3H2O has been prepared by the hydrothermal method and was characterized by elemental analysis, IR and UV spectra, TG-DTA and single crystal X-ray diffraction techniques. The asymmetric unit consists of [CoW12O40]6− and NO3− anions, the charge of which are counterbalanced by one octahedral [Co(H2O)6]2+ cation, a pyridinium [C5H6N]+ ion and 4H+ ions. The molecular structure of the title complex reveals a 3D supramolecular framework formed through intermolecular hydrogen bonds. This constitutes the first example in which a chiral architecture has been generated from achiral building blocks, where centrosymmetrically related cobalt octahedra and polyoxoanion tetrahedra are entangled through pairs of hydrogen bonds in a double helical way with a channel that houses a 1D water–NO3− double helix. This chiral POM shows good efficiency in the oxidation of common olefins in the presence of an environmentally benign oxidant, H2O2, under mild conditions.