Synthesis, structure elucidation, vibrational and thermal behavior study of new one-core dication molten-salt

Abstract

We decided to conduct the acid-base reaction of piperazine and sulfuric acid as a secondary diamine and diprotic acid, respectively. A new molten salt was obtained, which its structure elucidation was performed by FTIR, 1D NMR, 2D NMR, and mass spectrometry. In contrast to previous reports and our expectation, no characteristic signal was detected for the existence of hydrogen sulfate anion in 1H NMR of molten salt in DMSO‑d6. The 1H NMR of reactants, the new molten salt, and another derivative of this molten salt analyzed in the same deuterated solvent. Further support for the formation of 1H,4H-piperazine-N,N'-diium dication was concluded by an NMR study of its bromide derivative i.e., 1H,4H-piperazine-N,N'-diium dibromide. Based on the results of FTIR, NMR, pH, and titrimetry analyses, the formation of sulfate anion and the presence of an excess of sulfuric acid were excluded. The thermal behavior and thermal stability of new molten salt are also studied and reported.