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

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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 (C 11 H 19 N 2 S +) 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, C 11 H 19 N 2 S + ·C 8 H 7 O 2 -, (I), 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 4-bromobenzoate, C 11 H 19 N 2 S + ·C 7 H 4 BrO 2 -, (II), 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium 3,5-dinitrobenzoate, C 11 H 19 N 2 S + ·C 7 H 3 N 2 O 6 -, (III), bis(2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium) fumarate, 2C 11 H 19 N 2 S + ·C 4 H 2 O 4 2-,(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, 1.5C 11 H 19 N 2 S + ·0.5C 4 H 4 O 4 2- ·0.5C 4 H 5 O 4 -. 0.5C 11 H 18 N 2 S, (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 - NH 2 fragment of the cation are indistinguishable, indicating a significant contribution of the -NH - C=N + H 2 resonance form to the structure. The packing for (I)-(V) features a robust local R 2 2 (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 R 2 2 (8) loop results for both disorder components]. The anti H atom of the -NH 2 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.




Shaibah, M. A. E., Sagar, B. K., Yathirajan, H. S., Cordes, D. B., Slawin, A. M. Z., & Harrison, W. T. A. (2019). Hydrogen-bonded molecular salts of reduced benzothiazole derivatives with carboxylates: A robust (8) supramolecular motif (even when disordered). Acta Crystallographica Section E: Crystallographic Communications, 75, 167–174. https://doi.org/10.1107/S2056989018018224

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