Details

Autor(en) / Beteiligte

• Rauber, Daniel
• Philippi, Frederik
• Morgenstern, Bernd
• Zapp, Josef
• Kuttich, Björn
• Kraus, Tobias
• Welton, Tom
• Hempelmann, Rolf
• Kay, Christopher W.M.

Titel

Dynamics, cation conformation and rotamers in guanidinium ionic liquids with ether groups

Ist Teil von

• Journal of ionic liquids, 2023-12, Vol.3 (2), p.100060, Article 100060

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• •Novel ionic liquids based on the guanidinium cation are synthesized.•Structure-property relations are investigated in detail.•Ether side chain leads to higher melting point but accelerated dynamics.•Different conformations in solid and liquid state are found for ether and alkyl side chain.•Ether coordination increases the rotational barrier around the C-N bond of the guanidinium cation. Ionic liquids are modern materials with a broad range of applications, including electrochemical devices, the exploitation of sustainable resources and chemical processing. Expanding the chemical space to include novel ion classes allows for the elucidation of novel structure-property relationships and fine tuning for specific applications. We prepared a set of ionic liquids based on the sparsely investigated pentamethyl guanidinium cation with a 2-ethoxy-ethyl side chain in combination with a series of frequently used anions. The resulting properties are compared to a cation with a pentyl side chain lacking ether functionalization. We measured the thermal transitions and transport properties to estimate the performance and trends of this cation class. The samples with imide-type anions form liquids at ambient temperature, and show good transport properties, comparable to imidazolium or ammonium ionic liquids. Despite the dynamics being significantly accelerated, ether functionalization of the cation favors the formation of crystalline solids. Single crystal structure analysis, ab initio calculations and variable temperature nuclear magnetic resonance measurements (VT-NMR) revealed that cation conformations for the ether- and alkyl-chain-substituted are different in both the solid and liquid states. While ether containing cations adopt compact, curled structures, those with pentyl side chains are linear. The Eyring plot revealed that the curled conformation is accompanied by a higher activation energy for rotation around the carbon-nitrogen bonds, due to the coordination of the ether chain as observed by VT-NMR. [Display omitted]