On the structure of cetylpyridinium perchlorate: A combined XRD, NMR, IR and DFT study

Cetylpyridinium perchlorate has been synthesized and characterized by using the differential thermal analysis (DTA), X-ray powder diffraction (XRD) techniques, Fourier transform infrared spectroscopy (FT-IR), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The investigated salt melts con-gruently at 100 degrees C. The DTA and XRD results indicate that the cetylpyridinium perchlorate samples syn-thesized at different temperatures differ in crystallinity. It has been established that the crystallinity degree of the samples affects the decomposition temperature. The highest decomposition temperature (Td = 265 degrees C) is observed for the sample crystallized at 20 degrees C. Cetylpyridinium perchlorate crystallizes in the monoclinic crystal system with the cell parameters a = 20.31 A, b = 16.20 A, c = 7.25 A, b = 95.26 degrees, Z = 4. According to the DFT calculations, the interionic interactions in the structure are characterized by elec-tron transfer from the perchlorate anion to the cetylpyridinium cation. This explains a noticeable differ-ence in the 1H NMR chemical shifts of the hydrogen atoms in the ortho-position (-0.2 ppm) and the a -methylene group (-0.1 ppm) of the DMSO solutions of the cetylpyridinium perchlorate and chloride salts micelles. The electronic structure analysis of cetylpyridinium perchlorate and cetylpyridinium chloride in terms of the quantum theory of atoms-in-molecules and the analysis of non-covalent interactions with the reduced density gradient method have revealed the presence of strong interactions between the ions in the DMSO solution. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Cetylpyridinium perchlorate was synthesized and characterized using various analysis techniques. The crystallinity of the samples varied with different synthesis temperatures, affecting the decomposition temperature. The interionic interactions in the structure were characterized by electron transfer. The electronic structure analysis revealed strong interactions between ions in the solution.