| Summary: | The asymmetric unit of the title compound, C3H4N4O2·0.5H2O, comprises two whole molecules of 5-amino-1H-1,2,4-triazole-3-carboxylic acid in its zwitterionic form (proton transfer occurs from the carboxylic acid group to the N heteroatom at position 1), plus one water molecule of crystallization. The organic moieties are disposed into supramolecular layers linked by N—H...O and N—H...N hydrogen bonds parallel to the bc plane. Additional O—H...O and N—H...O hydrogen bonds involving the water molecules and the organic molecules lead to the formation of double-deck supramolecular arrangements which are interconnected along the a axis via π–π stacking [centroid–centroid distance = 3.507 (3) Å].
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