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, C7H7N2S+center dot HSO4-, (I), and the final product 2-iminio-2,3-dihydro-1,3-benzothiazole-6-sulfonate, C7H6N2O3S2, (II), both have the endocyclic N atom protonated; compound (I) exists as an ion pair and (II) forms a zwitterion. Intermolecular N-H center dot center dot center dot O and O-H center dot center dot center dot 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.