Reaction of diacetylmonoxime with morpholine N-thiohydrazide in the absence and in presence of a metal ion: Facile synthesis of a thiadiazole derivative with non-bonded S⋯S interaction

The condensation of diacetylmonoxime (damnx) with morpholine N-thiohydrazide (mth) in 1:1 molar ratio in ethanol (16 h) afforded a nitrogen–sulfur zwitterionic heterocyclic compound, N-(3,4-dimethyl-1,2,5-thiadiazole-2-ium-2-yl)morpholine-4-carbothioate (dtmc). However, the same reaction in presence of [Zn(OAc)2]·2H2O in ethanol under gentle reflux on (3 h) yielded the zinc complex, [Zn(Hdammthiol)(OAc)(H2O)]·H2O, where H2dammthiol (H2L2) is the thiol form of tridentate NNS donor thiohydrazone ligand, diacetylmonoxime morpholine N-thiohydrazone (Hdammth). Both the nitrogen–sulfur heterocyclic compound and the zinc complex have been characterized by elemental analyses, spectroscopy (IR, UV–Vis, 1H NMR and 13C NMR) and single crystal X-ray crystallography. It is noteworthy that the heterocyclic compound shows S⋯S interaction with distance 2.738 Å in its planar conformation. The heterocyclic compound forms two dimensional supramolecular sheets through C–H⋯O and π⋯π interactions while the zinc complex, with distorted square pyramidal geometry, forms 1D supramolecular chain. A mechanism has been proposed for the formation of nitrogen–sulfur heterocyclic compound.

The reaction of diacetylmonoxime with morpholine N-thiohydrazide under refluxing (16 h) conditions in ethanol afforded the zwitterionic nitrogen–sulfur heterocyclic compound N-(3,4-dimethyl-1,2,5-thiadiazole-2-ium-2-yl)morpholine-4-carbothioate (dtmc), with a non-bonded S⋯S interaction. This heterocyclic compound forms a 2D supramolecular sheet via C–H⋯O and π⋯π interactions. However, reaction of these two components in the presence of Zn(OAc)2·2H2O in ethanol yielded the zinc complex [Zn(Hdammthiol)(H2O)(OAc)]·H2O. A 1D supramolecular chain, diagonal to the ab plane, has been formed in this molecule, also by O–H····O hydrogen bonding. The zinc complex shows a blue emission in chloroform at room temperature.Figure optionsDownload as PowerPoint slide