4,15-Dimethyl-7,12-diazo-niatri-cyclo-[10.4.0.0(2,7)]hexa-deca-1(12),2,4,6,13,15-hexa-ene 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 di-pyridyls 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-methyl-pyridine 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 nitro-gen atoms by a tetra-methyl-ene bridge. Charge balance is provided by a pair of bromide anions, which are hydrogen bonded to a single water mol-ecule [D (O⋯Br) = 3.3670†(15) and 3.3856†(15)†à ]. The crystal structure of 1, details of an improved synthesis, and a full analysis of its NMR spectra are presented.