Crystal structure of 5-amino-4H-1,2,4-triazol-1-ium pyrazine-2-carboxylate: an unexpected salt arising from the decarboxylation of both precursors

Abstract

Both the 3-amino-2H,4H-1,2,4-triazolium cation and the pyrazine-2-carboxylate anion in the title salt, C2H5N4+·C5H3N2O2−, were formed by an unexpected decarboxylation reaction, from 5-amino-1H-1,2,4-triazole-3-carboxylic acid and pyrazine-2,3-dicarboxylic acid, respectively. The dihedral angle between the pyrazine ring (r.m.s. deviation = 0.008 Å) and the carboxylate group in the anion is 3.7 (3)°. The extended structure of the salt contains a supramolecular zigzag tape in which cations and anions are engaged in strong and highly directional N—H...N,O hydrogen bonds, forming R22(8) and R22(9) graph-set motifs. The packing between the tapes is mediated by π–π stacking interactions between the triazole and pyrazine rings.

Keywords

• crystal structure
• ionothermal synthesis
• decarboxylation
• triazolium salt
• hydrogen bonding
• π–π stacking interactions