The title compound, H3O+·C6H2N3O7 −, consists of one picrate anion and one oxonium cation. The oxonium cation is located on a crystallographic twofold axis and both its H atoms are disordered, each over two symmetry-equivalent positions with occupancy ratios of 0.75. The picrate anions are also located on twofold axes bis­ecting the phenolate and p-nitro groups. π–π inter­actions between the rings of the picrates [centroid-to-centroid distances of 3.324 (2) Å] connect the anions to form stacks along the a-axis direction. The stacks are further joined together by the protonated water mol­ecules through hydrogen bonds to form two-dimensional sheets extending parallel to the ab plane. The sheets are stacked on top of each other along the c-axis direction and connected through C—H⋯O inter­actions between the CH groups of the benzene rings and the picrate nitro groups, with C⋯O distances of 3.450 (2) Å.

The bis­(benzimidazol-1-yl)methane mol­ecule of the title compound, C15H12N4·2H2O, displays a trans conformation with a twofold axis running through the methylene C atom. Two adjacent water mol­ecules are bonded to this mol­ecule through O—H⋯N hydrogen bonds, forming a trimer. Adjacent trimers are connected together via C—H⋯O inter­actions, forming a chain running along the b-axis direction. Two such chains are joined together via π–π inter­actions [centroid–centroid distance = 3.556 (2) Å], forming double chains, which are connected via the water mol­ecules through C—H⋯O associations, forming a sheet structure. The sheets are stacked on top of each other along the a-axis direction and connected through O—H⋯O and C—H⋯O inter­actions, forming a three-dimensional ABAB layer network structure.

C 7 H 7 CdNO 7 ,triclinic, P1 (no. 2), a =7.0850(6) Å, b =7.5509(7) Å, c =10.713(1) Å, a =104.696(1)°, Source of materialCrystals of diaqua(5-nitrosalicylate)cadmium(II) were formed during an experiment to synthesize the mixed-ligand cadmium complex. As olution of cadmium acetate dihydrate (27 mg, 0.1 mmol) in 5m Lo fM eOH was added to aM eOH solution (3 mL) containing 3,5-dimethylpyrazole (19.2mg, 0.2 mmol) and 5-nitrosalicylic acid (36.6mg, 0.2 mmol), under continuous stirring. The solution was stirred for about 3h at room temperature, a small amount of precipitate formed, then af ew drops of concentrated ammonia was added till thep recipitate dissolved completely. The clear solution was filtered into the test tubeand after several days, colorless block crystals were obtained by slow evaporationofthe ammonia solution at ambient temperature. Experimental detailsAllHa toms attached to Ca toms were fixed geometrically and treated as riding with d(C-H) =0.93 Åwith U iso (H) =1.2 U eq (C). Ha toms of water molecule were located in difference Fourier mapand included in the subsequent refinement using restraints of d(O-H) =0.85(1) Åwith U iso (H) =1.5 U eq (O). In the last stage of refinement, they were treated as riding on the Oatom.