Five varieties of hydrogen bond in 1-formyl-3-thiosemicarbazide: an electron density study

Abstract

In an attempt to investigate the putative S-H…N hydrogen bond, we have studied the title compound, 1-formyl-3-thiosemicarbazide, which was revealed in a CSD search as a crystal structure which might show such an interaction. However, a redetermination of the structure at room temperature and careful analysis showed that the earlier study [Saxena et al. (1991). Acta Cryst. C47, 2374-2376] on which the CSD search was based was in error and that the possibility of an S-H…N hydrogen bond is negated. The presence of five other varieties of hydrogen bond (N-H…O, N-H…S, N-H…N, C-H…O, C-H…S) in the crystal packing prompted us to redirect our efforts and to undertake a study of the charge-density distribution at 90 K. The topological analysis of these five varieties of hydrogen bond was carried out with Bader's quantum theory of `atoms in molecules' and by applying Koch-Popelier's criteria. The analysis reveals that the hydrogen-bond strength is highest for N-H…O and lowest for C-H…S with N-H…S, N-H…N and C-H…O forming the middle order.