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The cation-cation π-π stacking is uncommon but it is essential for the understanding of some supramolecular structures. We explore theoretically the nature of non-covalent interaction occurring in the stacked structure within modeled clusters of 1,3-dimethylimidazolium and halide. The evidences of the energy decomposition analysis (EDA) and reduced density gradient (RDG) approach are different from those of common π-π interaction. Isosurfaces with RDG also illustrate the strength of the titled π-π interaction and their region. Additionally, we find that the occurrence of this interaction is attributed to a few C-H···X interactions, as depicted using atom in molecule (AIM) method. This work presents a clear picture of the typical cation-cation π-π interaction and can serve to advance the understanding of this uncommon interaction., (Copyright © 2015 Elsevier Inc. All rights reserved.)

In this paper, the structure of 1-carboxymethyl-3-methylimidazolium chloride was studied by X-ray diffraction, density functional theory, and FT-IR and Raman spectroscopic techniques for the first time. Title compound crystallizes in the orthorhombic space group Pca2(1) with the cell dimensions a=13.445 (6) Å, b=6.382 (3) Å, c=9.727 (5) Å and V=834.6 (7) Å(3). All the geometrical parameters have been calculated using by B3LYP with 6-311G++(d,p) basis set. Optimized geometries have been compared with the experimental data, and the hydrogen bond and short contact interactions were discussed. The vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were calculated at the same level. The observed bands were assigned based on the theoretical calculations. The scaled vibrational frequencies seem to coincide with the experimental data with acceptable deviations., (Copyright © 2012 Elsevier B.V. All rights reserved.)

In order to deepen the understanding of the cation-anion interaction in ionic liquids, the structures of cation, anions, and cation-anion ion-pairs of 1-allyl-3-methylimidazolium-based ionic liquids are optimized using density functional theory (DFT), and their most stable geometries are discussed. The structural parameters, hydrogen bonds and interaction energies of 1-allyl-3-methylimidazolium dicyanamide ([Amim]DCA), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), 1-allyl-3-methylimidazolium formate ([Amim]FmO) and 1-allyl-3-methylimidazolium acetate ([Amim]AcO) ion pairs are studied. The vibrational frequencies of [Amim]DCA and [Amim]Cl have been calculated and scaled values have been compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The title compound, C6H9N2O2+·Cl−·C6H8N2O2·H2O, contains one 2-(3-methyl-1 H-imidazol-3-ium-1-yl)acetate inner salt molecule, one 1-carboxymethyl-3-methyl-1 H-imidazol-3-ium cation, one chloride ion and one water molecule. In the extended structure, chloride anions and water molecules are linked via O-H...Cl hydrogen bonds, forming an infinite one-dimensional chain. The chloride anions are also linked by two weak C-H...Cl interactions to neighbouring methylene groups and imidazole rings. Two imidazolium moieties form a homoconjugated cation through a strong and asymmetric O-H...O hydrogen bond of 2.472 (2) Å. The IR spectrum shows a continuous D-type absorption in the region below 1300 cm−1 and is different to that of 1-carboxymethyl-3-methylimidazolium chloride [Xuan, Wang & Xue (2012). Spectrochim. Acta Part A, 96, 436-443]. [ABSTRACT FROM AUTHOR]

In this paper, 1,3-bis(carboxymethyl)imidazolium nitrate was prepared, and its structure was also determined by a single-crystal X-ray diffraction. Its FT-infrared and Raman spectra were measured and reported. The crystal structure and the type of O H…O hydrogen bonds were analyzed on the basis of the vibrational spectroscopy and Density Functional Theory (DFT) calculation. Additionally, thermal stability of 1,3-bis(carboxymethyl)imidazolium nitrate and its decomposition process were discussed. [ABSTRACT FROM AUTHOR]