Host–guest encapsulation of organosulphonate ligands into a host framework assembled from Keggin polyoxometalate anions and in situ generated organonitrogen cations

The synthesis and crystal structure of a novel supramolecular compound, formulated as (H2pesp)(H2pip)2[SiMo12O40] · 4H2O 1 (pesp2− = piperazine-1,4-bis(2-ethanesulfonic acid) anion, pip = piperazine), is described. Compound 1 is characterized by elemental analyses, infrared spectrum, thermogravimetric analysis, and single-crystal X-ray analysis. X-ray crystallography reveals that 1 displays a three-dimensional supramolecular framework constructed by [SiMo12O40]4− Keggin anions and in situ generated mix H2pip2+ and H2pesp ligands. In the structure of 1, [SiMo12O40]4− Keggin anions and in situ generated H2pip cations self-assemble into a hybrid porous host via intensive fourfold hydrogen bonds, within which the H2pesp precursor ligands are trapped as guests.