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

Abstract

The asymmetric unit of the title compound, C6H10N22+·2C4HO4−, comprises two hydrogen squarate (Hsq−; systematic name: 2-hydroxy-3,4-dioxocyclobutanolate) anions and a 2-(azaniumylmethyl)pyridinium dication. The squaric acid molecules each donate an H atom to the N atoms of the pyridine ring and the aminomethyl units of a 2-(aminomethyl)pyridine molecule, forming the 1:2 salt. The Hsq− anions are linked by strong O—H...O hydrogen bonds and an N—H...O hydrogen bond links the 2-(azaniumylmethyl)pyridinium cation to one of the squaric acid anions. The crystal structure features additional N—H...O and O—H...O hydrogen bonds, π–π stacking and unusual weak C—O...π(ring) interactions.

Keywords

• crystal structure
• 2-(azaniumylmethyl)pyridinium
• squaric acid
• hydrogen bonding