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. 2020 Aug 18;76(Pt 9):1467-1471.
doi: 10.1107/S2056989020011147. eCollection 2020 Sep 1.

4,15-Dimethyl-7,12-diazo-niatri-cyclo-[10.4.0.02,7]hexa-deca-1(12),2,4,6,13,15-hexa-ene dibromide monohydrate

Edward J Behrman  1 , Alexandar L Hansen  2 , Chunhua Yuan  2 , Sean Parkin  3
Affiliations

4,15-Dimethyl-7,12-diazo-niatri-cyclo-[10.4.0.02,7]hexa-deca-1(12),2,4,6,13,15-hexa-ene dibromide monohydrate

Edward J Behrman et al. Acta Crystallogr E Crystallogr Commun. .

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.

Keywords: atropisomer; crystal structure; synthesis; viologen.

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Figures

Figure 1
Figure 1
A view of 1 showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds between water and Br− are shown as dashed lines.
Figure 2
Figure 2
A packing plot of 1 viewed down the crystallographic a axis. Hydrogen bonds between water and Br− are shown as dashed lines, while weaker C—H⋯Br inter­actions are shown as dotted lines.
Figure 3
Figure 3
Analysis of 2-D NMR spectra: (a) HSQC and HMBC resonance assignments, (b) COSY resonance assignments. Peaks marked by an asterisk correspond to water or multiple quantum artifacts. 1-D traces are shown to the left and top of the figure.
See this image and copyright information in PMC

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