title: Bis[2-(2,4-dinitro-benz-yl)pyridinium] biphenyl-4,4'-disulfonate trihydrate.
abstract: 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 inter-acting head-to-head through centrosymmetric cyclic bis-(water)-bridged hydrogen-bonding associations [graph set R(4) (4)(11)], forming chains. The 2-(2,4-dinitro-benz-yl)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 inter-actions [minimum ring centroid separation = 3.8441 (13) Å].
authors.forename: Graham
authors.initials: G
authors.lastname: Smith
authors.forename: Urs D
authors.initials: UD
authors.lastname: Wermuth
authors.forename: David J
authors.initials: DJ
authors.lastname: Young