Fernandes José A, Liu Bing, Tomé João P C, Cunha-Silva Luís, Almeida Paz Filipe A
Acta Crystallogr Sect E Struct Rep Online. 2011 Aug 1;67(Pt 8):o2073-4. doi: 10.1107/S160053681102811X. Epub 2011 Jul 23.
The asymmetric unit of the title compound, C(3)H(4)N(4)O(2)·0.5H(2)O, comprises two whole mol-ecules of 5-amino-1H-1,2,4-triazole-3-carb-oxy-lic acid in its zwitterionic form (proton transfer occurs from the carb-oxy-lic acid group to the N hetero-atom at position 1), plus one water mol-ecule of crystallization. The organic moieties are disposed into supra-molecular 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 mol-ecules and the organic mol-ecules lead to the formation of double-deck supra-molecular arrangements which are inter-connected along the a axis via π-π stacking [centroid-centroid distance = 3.507 (3) Å].
标题化合物C(3)H(4)N(4)O(2)·0.5H(2)O的不对称单元包含两个两性离子形式的5-氨基-1H-1,2,4-三唑-3-羧酸分子（质子从羧酸基团转移至1位的N杂原子），外加一个结晶水分子。有机部分通过与bc平面平行的N-H⋯O和N-H⋯N氢键排列成超分子层。涉及水分子和有机分子的额外O-H⋯O和N-H⋯O氢键导致形成双层超分子排列，其沿a轴通过π-π堆积相互连接[质心-质心距离 = 3.507 (3) Å]。
