Reinvestigation of zinc(II) complexation by 2-thiophenecarboxylic hydrazide: X-ray structure of tris(2-thiophenecarboxyhydrazide)zinc(II) tetrachlorozincate(II) di(ethanol) and vibrational spectroscopy of its decomposition product

Reaction of ZnCl2 and 2-thiophenecarboxylic hydrazide (tch), in ethanol resulted in the crystalline product [Zn(tch)3][ZnCl4] · 2EtOH, which slowly decomposes losing solvent molecules. The structure of the first compound has been determined by the single crystal X-ray method. Analysing the IR spectra of both compounds it has been found that the complex [Zn(tch)3]2+ cation and [ZnCl4]2− anion are preserved after crystal decomposition. Vibrational spectra of the obtained substances were interpreted with the assistance of DFT calculations and metal isotope as well as deuterium replacement.