Hydrogen-bonded molecular salts of reduced benzothiazole derivatives with carboxylates: a robust R_2^2(8) supramolecular motif (even when disordered)

Mohammed A. E. Shaibah, Belakavadi K. Sagar, Hemmige S. Yathirajan, David B. Cordes, Alexandra M. Z. Slawin, William T. A. Harrison* (Corresponding Author)

*Corresponding author for this work

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The syntheses and structures of five mol­ecular salts of protonated 4,4,7,7-tetra­methyl-3a,5,6,7a-tetra­hydro­benzo­thia­zol-2-yl­amine (C11H19N2S+) with different deprotonated carb­oxy­lic acids (4-methyl­benzoic acid, 4-bromo­benzoic acid, 3,5-di­nitro­benzoic acid, fumaric acid and succinic acid) are reported, namely 2-amino-4,4,7,7-tetra­methyl-4,5,6,7-tetra­hydro-1,3-benzo­thia­zol-3-ium 4-methyl­benzoate, C11H19N2S+·C8H7O2−, (I), 2-amino-4,4,7,7-tetra­methyl-4,5,6,7-tetra­hydro-1,3-benzo­thia­zol-3-ium 4-bromo­benzoate, C11H19N2S+·C7H4BrO2, (II), 2-amino-4,4,7,7-tetra­methyl-4,5,6,7-tetra­hydro-1,3-benzo­thia­zol-3-ium 3,5-di­nitro­benzoate, C11H19N2S+·C7H3N2O6, (III), bis­(2-amino-4,4,7,7-tetra­methyl-4,5,6,7-tetra­hydro-1,3-benzo­thia­zol-3-ium) fumarate, 2C11H19N2S+·C4H2O42−,(IV), and the 1:1 co-crystal of bis­(2-amino-4,4,7,7-tetra­methyl-4,5,6,7-tetra­hydro-1,3-benzo­thia­zol-3-ium) succinate and 2-amino-4,4,7,7-tetra­methyl-4,5,6,7-tetra­hydro-1,3-benzo­thia­zol-3-ium hydrogen succin­ate 4,4,7,7-tetra­methyl-3a,5,6,7a-tetra­hydro­benzo­thia­zol-2-yl­amine, 1.5C11H19N2S+·0.5C4H4O42−·0.5C4H5O4. 0.5C11H18N2S, (V). In every case, the cation protonation occurs at the N atom of the thia­zole ring and the six-membered ring adopts a half-chair conformation (in some cases, the deviating methyl­ene groups are disordered over two sets of sites). The C—N bond lengths of the nominal –NH+=C—NH2 fragment of the cation are indistinguishable, indicating a significant contribution of the –NH—C=N+H2 resonance form to the structure. The packing for (I)–(V) features a robust local R22(8) loop motif in which the cation forms two near-linear N—H⋯O hydrogen bonds from the N+—H group and syn H atom of the amine group to the carboxyl­ate group of an adjacent anion [(V) shows disorder of one of these bonds over N—H⋯O and N⋯H—O contributors but the same R22(8) loop results for both disorder components]. The anti H atom of the –NH2 group also forms an N—H⋯O hydrogen bond, which results in [001] chains in (I) and (II), isolated centrosymmetric tetra­mers in (III) and [100] chains in (IV) and (V). Hirshfeld fingerprint plots and contact percentages for the different types of contacts of the cations are discussed.
Original languageEnglish
Pages (from-to)167-174
Number of pages8
JournalActa Crystallographica Section E: Crystallographic Communications
Issue number2
Early online date8 Jan 2019
Publication statusPublished - 1 Feb 2019

Bibliographical note

MAES thanks the University of Mysore for provision of research facilities.

Funding information
HSY thanks UGC for the award of a UGC–BSR Faculty Fellowship for three years. BKS thanks the UGC for the award of a Rajeev Gandhi fellowship.


  • benzothiazole
  • hydrogen bond
  • molecular salt
  • crystal structure


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