N,N-Dimethoxyimidazolium Derivatives as Ion Pair Constituents of Energetic Redox Couples : Model Studies by Thermal Analysis and Crystallography

Lukas Fliri*, Thomas Gelbrich, Ulrich J. Griesser, Gabriel Partl, Felix R.S. Purtscher, Sandro Neuner, Kevin Erharter, Klaus Wurst, Volker Kahlenberg, Doris E. Braun, Thomas S. Hofer, Albert Rössler, Herwig Schottenberger*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

By utilizing an expedient anion exchange protocol and starting with an improved synthesis of 2-azido-1,3-dimethoxyimidazolium hexafluorophosphate, a series of six metathetical salts, including the energetic nitrate and perchlorate as well as the halides, was prepared. We focused on the crystallographic and thermal characterization of these compounds, representing intrinsically reactive hybrid organic / inorganic salts, and conducted a small comparative study with the related 2-methyl-1,3-dimethoxyimidazolium salts. The latter compounds were expected to thermally disintegrate less sluggishly since the covalent azido-group as intrinsic blasting initiator is missing. Both 2-azido- and 2-methylimidazolium nitrate exhibit a very sharp thermal onset of complete disintegration. In contrast, the respective perchlorates display a continuous thermogravimetric weight loss over a broad temperature range. Additionally, X-ray single crystal structure determinations were performed for eight of the new compounds as well as for two 2-azido-1,3-dimethoxyimidazolium salts with a mixed anion composition. Phase purity was also checked for five of the congeners using powder X-ray diffraction (Pawley fitting). Notably, in the 2-azido-imidazolium cation, the intra-ring bonds of the N1−C2 type were found to be significantly shorter than N1−C4 type bonds, and a characteristic asymmetry between the two N1−C2−N(azido) bond angles was observed. The experimental cation geometry was reproduced by DFT calculations on selected compounds.

Original languageEnglish
Number of pages13
JournalZeitschrift fur Anorganische und Allgemeine Chemie
Early online date22 Nov 2020
DOIs
Publication statusPublished - 20 Jan 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • 1,3-Dimethoxyimidazolium
  • 2-Azido-imidazolium
  • anion metathesis
  • comparative crystallography
  • energetic salts

Fingerprint Dive into the research topics of 'N,N-Dimethoxyimidazolium Derivatives as Ion Pair Constituents of Energetic Redox Couples : Model Studies by Thermal Analysis and Crystallography'. Together they form a unique fingerprint.

Cite this