Penta­guanidinium mono­hydrogen­diphospho­penta­molybdate(VI) 2.5-hydrate, (CH₆N₃)₅[HP₂Mo₅O₂₃]·2.5H₂O: hydrogen bonding and [pi]-stacking in guanidinium cations

In the title compound, each singly protonated diphospho­penta­molyb­date(VI) anion retains the typical geometry of a ring of five edge-sharing MoO₆ octa­hedra, except for one corner-sharing link. Two capping PO₄ tetra­hedra share corners with the five octa­hedra. Despite being surrounded by an extensive network of hydrogen bonds, predominantly from the guanidinium cations, short P-O-H...O=P contacts associate the anions into infinite columns generated by the c-glide.