Crystal structure and Hirshfeld surface analysis of two organic salts based on 1,3,4-thia­diazole derivatives

During attempts to achieve inter­action between 2-amino-5-ethyl-1,3,4-thia­diazole with oxalyl chloride and 5-mercapto-3-phenyl-1,3,4-thia­diazol-2-thione with various diacid anhydrides, we obtained two co-crystals (organic salts), namely, 2-amino-5-ethyl-1,3,4-thia­diazol-3-ium hemioxalate, C(4)H(8)N(3)S(+)·0.5C(2)O(4) (2−), (I), and 4-(di­methyl­amino)­pyridin-1-ium 4-phenyl-5-sulfanyl­idene-4,5-di­hydro-1,3,4-thia­diazole-2-thiol­ate, C(7)H(11)N(2) (+)·C(8)H(5)N(2)S(3) (−), (II). Both solids were investigated by single-crystal X-ray diffraction and by Hirshfeld surface analysis. An infinite one-dimensional chain along [100] is generated through O—H⋯O inter­actions between the oxalate anion and two 2-amino-5-ethyl-1,3,4-thia­diazol-3-ium cations in compound (I), and a three-dimensional supra­molecular framework is generated through C—H⋯O and π–π inter­actions. In compound (II), an organic salt is formed by a 4-phenyl-5-sulfanyl­idene-4,5-di­hydro-1,3,4-thia­diazole-2-thiol­ate anion and a 4-(di­methyl­amino)­pyridin-1-ium cation, which are combined by an N—H⋯S hydrogen-bonding inter­action, forming a zero-dimensional structural unit. As a result of inter­molecular π–π inter­actions, the structural units are combined into a one-dimensional chain running along the a-axis direction.