Crystal structure of 2-ethyl-4-methyl-1-(2-oxido-3,4-dioxocyclobut-1-en-1-yl)-1H-imidazol-3-ium

Abstract

In the crystal of the inner salt of the title compound, N—H⋯O and C—H⋯O hydrogen bonds form an (9) ring motif.

1-(Imidazo[1,2-a]pyridin-1-ium-1-yl)-2,3,4-trioxocyclobutan-1-ide

“…A simple method for the preparation of pyridinium ylides of squaric acid, by heating the starting compounds in acetic anhydride, has been described by Schmidt et al [7]. Employing this procedure, the reaction of 2-ethyl-4-methylimidazole with squaric acid resulted in the formation of an ylide, which was identified as a candidate to develop a non-linear optical material [8]. By applying this method, 1 was obtained from 2 and squaric acid (5) in acetic anhydride (Scheme 2).…”

“…Disappointingly, all these structures were measured at room temperature. Furthermore, the two structures most similar to 1, which are imidazole derivatives [8,9], are rather imprecise; they have wR2 values of 0.25 and 0.27, respectively, so that a detailed comparison of molecular dimensions is ruled out. A more precise structure is provided by [10], which has a pyridinium ring at C4.…”

Crystal structure of 2-(azaniumylmethyl)pyridinium bis(hydrogen squarate)

“…properties and that they can be used as electron acceptors in photo-sensitive devices (Korkmaz et al, 2016).…”