Structure of 6-oxo-1,6-dihydro-3,4'-bipyridine-5-carbonitrile hydrogen bromide.

5-Cyano-6-oxo-1,6-dihydro-3,4'-bipyridinium bromide, C11H8N3O+.Br-, Mr = 278.11, triclinic, P1, a = 7.827 (2), b = 9.796 (2), c = 15.548 (4) A, alpha = 76.53 (2), beta = 75.40 (2), gamma = 74.36 (2) degrees, V = 1093.4 (4) A3, Z = 4, Dx = 1.689 Mg m-3, lambda (Mo K alpha) = 0.71073 A, mu = 3.70 mm-1, F(000) = 552, T = 293 K, R = 0.084 for 3989 observed reflections. The bipyridinium ions are planar, the C(2)-C(1)-C(1')-C(2') torsion angles being -3.3 (10) and 2.2 (11) degrees for molecules (1) and (2), respectively. The symmetry-independent bipyridinium ions are assembled in separate chains by hydrogen-bonding Br bridges [respective distances: Br(1)...N(3) 3.227 (6); Br(1)...N(4') 3.374 (6); Br(2)...N(3*) 3.263 (5); Br(2)...N(4') 3.540 (7) A] and by forming N...O hydrogen bonds between pyridinium NH groups and keto O atoms, the N(4')...O(4) and N(4')...O(4') distances being 2.835 (7) and 2.706 (7) A, respectively. These chains are connected by the series of stacking interactions with an average C...C distance of 3.5 A.