4,15-Dimethyl-7,12-diazo­niatri­cyclo­[10.4.0.0(2,7)]hexa­deca-1(12),2,4,6,13,15-hexa­ene dibromide monohydrate

The title compound, C(16)H(20)N(2) (2+)·2Br(−)·H(2)O (1) is a member of the class of compounds called viologens. Viologens are quaternary salts of di­pyridyls and are especially useful as redox indicators as a result of their large negative one-electron reduction potentials. Compound 1 consists of a dication composed of a pair of 4-methyl­pyridine rings mutually joined at the 2-position, with a dihedral angle between the pyridine rings of 62.35 (4)°. In addition, the rings are tethered via the pyridine nitro­gen atoms by a tetra­methyl­ene bridge. Charge balance is provided by a pair of bromide anions, which are hydrogen bonded to a single water mol­ecule [D (O⋯Br) = 3.3670 (15) and 3.3856 (15) Å]. The crystal structure of 1, details of an improved synthesis, and a full analysis of its NMR spectra are presented.