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A series of 1,2-dimethylimidazolium ionic liquids bearing a hexadecyl alkyl chain are thoroughly examined via X-ray crystallography. The crystal structures reveal several key variations in the non-covalent interactions in the lipid-like salts. Specifically, distinct cation–cation π interactions are observed when comparing the bromide and iodide structures. Changing the anion to bis(trifluoromethane)sulfonimide (Tf 2 N − ) changes these cation–cation π interactions with anion⋯π interactions. Additionally, several well-defined geometries of the cations are noted based on torsion and core-plane angles of the alkyl chains. Hirshfeld surface analysis is used to distinguish the interactions and geometries in the solid state, helping to reveal characteristic structural fingerprints for the compounds. The solid-state structures of the ionic liquids are correlated with the solution-state structures through UV-vis spectroscopic studies, further emphasizing the importance of the π interactions in the formation of aggregates. Finally, we investigated the thermal properties of the ionic liquids, revealing complex phase transitions for the iodide-containing species. These phase transitions are further rationalized via the analysis of the data gathered from the structures of the other crystallized salts. 

The title salt, C 4 H 6 N 3 O 2 + ·Cl − , exhibits multiple hydrogen-bonding interactions involving the nitroimidazolium cation and the chloride anion. Strong hydrogen bonds between the amine hydrogen atom and the chloride anion link the ionic moieties. Of note, with respect to H...Cl interactions, the central aromatic hydrogen atom displays a shorter interaction than the other aromatic hydrogen atom. Finally, interactions are observed between the nitro moiety and methyl H atoms. While no π–π stacking is observed, anion-π interactions are present. The crystal was refined as a two-component twin. 

Abstract Two crystals incorporating the thiamine·HCl cation and the fluorinated anion 1,3-disulfonylhexafluoropropyleneimide have been characterized via single-crystal X-ray diffraction. The host-guest interactions of thiamine with the anions are analyzed and characterized using Hirshfeld surface analysis. The cations in both structures form a dimer in the solid-state via reciprocal hydrogen bonding through the amine and hydroxyl moieties. Additional investigation into the interactions responsible for dimer formation found that the sulfur atom in the thiazolium ring interacting with several hydrogen atoms to form stabilizing interactions. These interactions in the dimer are further analyzed using reduced density gradient analysis and the results are correlated to the fingerprint plots derived from the Hirshfeld surfaces. Moreover, specific interactions are observed from the cyclical anions, with both the fluorine and sulfonyl oxygen atoms participating in bridging interactions, displaying the diverse host-guest properties of thiamine. 

Numerous non-covalent interactions link together discrete molecules in the crystal structure of the title compound, 2C 20 H 26 N 2 O 2 2+ ·4Cl − ·H 2 O {systematic name: 4-[(5-ethenyl-1-azoniabicyclo[2.2.2]octan-2-yl)(hydroxy)methyl]-6-methoxyquinolin-1-ium dichloride hemihydrate}. A combination of hydrogen bonding between acidic H atoms and the anions in the asymmetric unit forms a portion of the observed hydrogen-bonded network. π–π interactions between the aromatic portions of the cation appear to play a role in the formation of the long-range ordering. One ethylene double bond was found to be disordered. The disorder extends to the neighboring carbon and hydrogen atoms.