Abstract
The title compound, C16H20N2 2+·2Br-·H2O (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) Å]. The crystal structure of 1, details of an improved synthesis, and a full analysis of its NMR spectra are presented.
Highlights
The title compound, C16H20N22+Á2BrÀÁH2O (1) is a member of the class of compounds called viologens
Charge balance is provided by a pair of bromide anions, which are hydrogen bonded to a single water molecule [DOÁ Á ÁBr = 3.3670 (15) and 3.3856 (15) A ]
Viologens are quaternary salts of dipyridyls, which have proven useful as redox indicators as a result of their large negative one-electron reduction potentials (Anderson & Patel, 1984)
Summary
The title compound (1) is a member of the class of compounds called viologens. Viologens are quaternary salts of dipyridyls, which have proven useful as redox indicators as a result of their large negative one-electron reduction potentials (Anderson & Patel, 1984). We found that the literature synthesis of 4,40-dimethyl-2,20-dipyridyl-N,N0-tetramethylene dibromide, i.e., 1 (Spotswood & Tanzer, 1967) could be improved by a change in the solvent. Spotswood & Tanzer (1967) give general directions for the syntheses of a series of bridged dimethyl 2,20-dipyridyl salts. Our attempts to make the title compound by their directions failed; only a salt of the starting dipyridyl was recovered. The addition of nitrobenzene to the solvent gave satisfactory yields of the product in a reasonable time (see Synthesis and crystallization section). Hydrogen bonds between water and BrÀ are shown as dashed lines
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