Computational NMR Study of Ion Pairing of 1-Decyl-3-Methyl-Imidazolium Chloride in Molecular Solvents

Structural Features of the [C4mim][Cl] Ionic Liquid and Its Mixtures with Water: Insight from a 1H NMR Experimental and QM/MD Study

“…These results are in line with the observed decrease of the chemical shift of atom H 2 with the increasing molar fraction of water as can be seen in Figure1b. In systems J and M with low averaged number of chloride anions near the C 2 −H 2 moiety, a substantial increase in the shielding constant is predicted by as much as 1.3 ppm as compared to the value computed for the neat IL, system G. The present results are in line with the previous observations that the presence or the absence of the hydrogen bonding between the C 2 −H 2 group and the chloride anion is the main factor determining the H 2 shielding constant of the imidazolium cation in the liquid phase 49. Our computational results in Table2thus allow concluding that the observed monotonically decreasing chemical shift of the H 2 atom with the increasing content of water in the mixture as illustrated in Figure1bis due to the gradual breakdown of the hydrogen bonding between the C 2 −H 2 moiety of imidazolium cations and chloride anions.…”

“…44 We have employed classical MD simulations along with a combined quantum mechanics/ molecular mechanics (QM/MM) model to study various NMR parameters 45−48 and lately addressing ion pairing in the solutions of [C10mim][Cl] IL where solvents differ in polarity and capabilities for hydrogen bonding. 49 In this work, this computationally expensive yet accurate computational technique is applied in order to gain molecular-level insight into structural organization of [C4mim][Cl]/water mixtures reflecting experimental NMR data in Figure 1.…”

“…Our computational results in Table2thus allow concluding that the observed monotonically decreasing chemical shift of the H 2 atom with the increasing content of water in the mixture as illustrated in Figure1bis due to the gradual breakdown of the hydrogen bonding between the C 2 −H 2 moiety of imidazolium cations and chloride anions. Notably, imidazolium chloride ILs are known to eventually dissociate into free fully solvated ions at the conditions of infinite dilution in an aqueous solution 49.…”