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

Abstract

The title compound, C16H20N2 2+·2Br−·H2O (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.