Bis[2-(2,4-dinitro­benz­yl)pyridinium] biphenyl-4,4′-disulfonate trihydrate

In the structure of the title salt, 2C(12)H(10)N(3)O(4) (+)·C(12)H(8)O(6)S(2) (2−)·3H(2)O, determined at 173 K, the biphenyl-4,4′-disulfonate dianions lie across crystallographic inversion centres with the sulfonate groups inter­acting head-to-head through centrosymmetric cyclic bis­(water)-bridged hydrogen-bonding associations [graph set R (4) (4)(11)], forming chains. The 2-(2,4-dinitro­benz­yl)pyridinium cations are linked to these chains through pyridinium–water N—H⋯O hydrogen bonds and a two-dimensional network is formed through water bridges between sulfonate and 2-nitro O atoms, while the structure also has weak cation–anion π–π aromatic ring inter­actions [minimum ring centroid separation = 3.8441 (13) Å].