2,3-Dihydro-1,3-benzothiazol-2-iminium monohydrogen sulfate and 2-iminio-2,3-dihydro-1,3-benzothiazole-6-sulfonate: a combined structural and theoretical study.

The 2-aminobenzothiazole sulfonation intermediate 2,3-dihydro-1,3-benzothiazol-2-iminium monohydrogen sulfate, C(7)H(7)N(2)S(+).HSO(4)(-), (I), and the final product 2-iminio-2,3-dihydro-1,3-benzothiazole-6-sulfonate, C(7)H(6)N(2)O(3)S(2), (II), both have the endocyclic N atom protonated; compound (I) exists as an ion pair and (II) forms a zwitterion. Intermolecular N-H...O and O-H...O hydrogen bonds are seen in both structures, with bonding energy (calculated on the basis of density functional theory) ranging from 1.06 to 14.15 kcal mol(-1). Hydrogen bonding in (I) and (II) creates DDDD and C(8)C(9)C(9) first-level graph sets, respectively. Face-to-face stacking interactions are observed in both (I) and (II), but they are extremely weak.