organic compounds
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The anion of the title compound, C5H6N+·C5H2NO4S−, is approximately planar, with the carboxylate and nitro group planes forming dihedral angles of 7.5 (3) and 3.5 (3)°, respectively, with the thiophene ring. In the crystal structure, the cations and anions are linked into a two-dimensional network parallel to (011) by N—HO and C—HO hydrogen bonds.