title: 2',6'-Bis(4-carb-oxy-phen-yl)-4,4'-bipyridin-1-ium nitrate 0.25-hydrate.
abstract: In the title compound, C(24)H(17)N(2)O(4) (+)·NO(3) (-)·0.25H(2)O, the central pyridine ring of the 2',6'-bis-(4-carb-oxy-phen-yl)-4,4'-bipyridin-1-ium cation is almost coplanar with one benzene ring [dihedral angle = 1.03 (5)°], while it makes dihedral angles of 9.59 (5)° with the other benzene ring and 13.66 (6)° with the pyridinium ring. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds link the cations and nitrate anions into a sheet in the (302) plane. The crystal structure also exhibits π-π inter-actions between the central pyridine ring and the benzene rings of neighboring mol-ecules [centroid-centroid distance = 3.6756 (13) Å].
authors.forename: Yaping
authors.initials: Y
authors.lastname: Li
authors.forename: Hu
authors.initials: H
authors.lastname: Zang
authors.forename: Guanfang
authors.initials: G
authors.lastname: Su