The effect of the anion size and electronegativity of halide-based anions (Cl − , Br − , I − , and BF 4 − ) on the interionic interaction in 1-ethyl-3-methylimidazolium-based ionic liquids (ILs) C 2 mim X (X = Cl, Br, I, and BF 4 ) is studied by a combined approach of experiments (Raman, IR, UV−vis spectroscopy) and quantum chemical calculations. The fingerprint region of the Raman spectra of these C 2 mim X ion-pairs provides evidence of the presence of the conformational isomerism in the alkyl chain of the C 2 mim + cation. The Raman and IR bands of the imidazolium C 2 −H stretch vibration for C 2 mim X (X = Cl, Br, I, and BF 4 ) were noticeably blue-shifted with the systematic change in size of anions and the electronegativity. The observed blue shift in the C 2 −H stretch vibration follows the order C 2 mim BF 4 > C 2 mim I > C 2 mim Br > C 2 mim Cl, which essentially indicates the strong hydrogen bonding in the C 2 mim Cl ion-pair. DFT calculations predict at least four configurations for the cation−anion interaction. On the basis of relative optimized energies and basis-setsuperposition-error (BSSE) corrected binding energies for all ion-pair configurations, the most active site for the anion interaction was found at the C 2 H position of the cation. Besides information about the C 2 H position, our DFT results give insights into the anion interaction with the ethyl and methyl chain of the cation, which was also confirmed experimentally [Chem. Commun. 2015, 51, 3193]. The anion interaction at the C 2 H site of the cation favors a planar geometry in C 2 mim X for X = Cl, Br, and I; however, for BF 4 , the system prefers a nonplanar geometry where the anion is located over the imidazolium ring. TD-DFT results were used to analyze the observed UV−vis absorption spectra in a more adequate way giving insights into the electronic structure of the ILs. Overall, a reasonable correlation between the observed and the DFT-predicted results is established.

We report for the first time self-assembly of an acyl-thiourea based sensor, N-{(6-methoxy-pyridine-2-yl) carbamothioyl}benzamide (NG1) to panchromatic fluorescent fibres and its dual-sensing properties for the sequential detection of Cu2+ ions...

The influence of the length of the alkyl chain and water molecules on the hydrogen-bond interaction of the chloride anion and imidazolium-based cation of the ionic liquid (IL) C_nmim Cl...

Hydrogen energy has received significant attention in the renewable energy sector due to its high energy density and environmentally friendly nature. For the efficient hydrogen generation from water, the hydrogen evolution reaction (HER) has to be optimized, which requires a highly efficient electrocatalyst. In this work, a hybrid structure of the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (C2mim TfO) and (TiO2) n nanoclusters with n = 2–12 has been investigated in the pursuit of new catalyst materials for effective HER. We have employed state-of-the-art density functional theory (DFT) computations to depict the HER catalytic performance of IL/(TiO2) n hybrid systems through Gibbs free energy (ΔG) and an exchange-current-based “volcano” plot. We have explored the effect of the TiO2 nanoclusters on the structural and electronic characteristics of the IL, calculating the adsorption energy, the energies of the highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO), the HOMO–LUMO band gap E g, and the work function ϕ. The variation in size of the TiO2 nanocluster in the IL/(TiO2) n hybrid system was found to have a significant influence on the electronic properties. The obtained results suggest that the ΔG of the hydrogen adsorption is remarkably close to the ideal value (0 eV) for the IL/(TiO2)5 system, which also reflects from the volcano plot, suggesting that this complex is the best HER catalyst among the studied systems; it might be even better than the traditional Pt-based catalyst. Thus, the present work suggests ways for the experimental realization of low-cost and multifunctional IL-based hybrid catalysts for clean and renewable hydrogen energy production.