Polyanionic clusters embedded in lattice-type hydrogen bonding networks involving in situ bond activation and coupling of organic cations

Abstract

Two inorganic–organic supramolecular polyoxometalates, (H₂chtpy)₂[SiW₁₂O₄₀] (1) (chtpy = 1,3,4,6-tetra(4-pyridyl)cyclohexane-1,3-diol) and [Co(Hbztpy)₂]H[AlW₁₂O₄₀]·3H₂O (2) (bztpy = 1,2,4,5-tetra(4-pyridyl)benzene), have been hydrothermally synthesized and characterized. Both of them consist of complex supramolecular interactions between inorganic polyanions and organic cations. During the formation process of 1 and 2, in situ organic reactions involving C–C coupling through dehydrogenative cyclodimerization of two flexible 1,3-bis(4-pyridyl)propane (bpp) molecules were observed. The tetradentate pyridyl chtpy and bztpy molecules serve as 4-connected nodes to enrich the structural topologies of 1 and 2. The typical centered N–H⋯N (N⋯N = 2.6–2.7 Å) hydrogen bonding interactions link the organic cations to form grid-type networks for capturing the pseudo-spherical Keggin-type anions. The pH values of the reaction solutions are important for the intermolecular C–C coupling of the organic molecules, and their transformation mechanisms are discussed.