Supramolecular aggregation in 4,4'-bipyridin-1,1'-ium dichloride, 4,4'-bipyridin-1,1'-ium dinitrate and 4,4'-bipyridin-1-ium bromide.

4,4'-Bipyridin-1,1'-ium dichloride [C(10)H(10)Cl(2)N(2) (I)] and 4,4'-bipyridin-1,1'-ium dinitrate [C(10)H(10)N(4)O(6) (II)] have been prepared and the crystal structures determined at 90.0 (2) K. Molecules of (I) are linked by two chlorine-bridged, three-centered N-H...Cl hydrogen bonds into chains along the b axis. The chains are coupled by weak C-H...Cl interactions into a molecular ladder along the c direction. In (II) each nitrate is coordinated to four bipyridinium ions through the interplay of the N-H...O and C-H...O contacts, resulting in a three-dimensional zigzag sheet on the ab plane. The sheets stack along the c axis. In 4,4'-bipyridin-1-ium bromide monohydrate [C(10)H(9)N(2)(+).Br(-).H(2)O (III)] the bipyridinium ions are linked by three-center N-H.N' hydrogen bonds in a head-to-tail fashion to form chains along the b axis. The chains are linked by C-H...Br and C-H...OH2 into a three-dimensional framework.