4-(3,5-Dimethyl-1H-pyrazol-4-ylmethyl)-3,5-dimethyl-1H-pyrazol-2-ium dihydrogen phosphate: a combined X-ray and DFT study.

The molecular structure of the title salt, C(11)H(17)N(4)(+).H(2)PO(4)(-), has been determined from single-crystal X-ray analysis and compared with the structure calculated by density functional theory (DFT) at the BLYP level. The crystal packing in the title compound is stabilized primarily by intermolecular N-H...O, O-H...N and O-H...O hydrogen bonds and pi-pi stacking interactions, and thus a three-dimensional supramolecular honeycomb network consisting of R(4)(2)(10), R(4)(4)(14) and R(4)(4)(24) ring motifs is established. The HOMO-LUMO energy gap (1.338 eV; HOMO is the highest occupied molecular orbital and LUMO is the lowest unoccupied molecular orbital) indicates a high chemical reactivity for the title compound.