IR and X-ray Study of Polymorphism in 1-Alkyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imides

Abstract

The crystal structure of [C(n)mim]NTf(2) (n = 2, 4, 6) was studied for the first time simultaneously by X-ray diffraction method and IR spectroscopy. The temperature-dependent IR spectrum for crystalline [C(4)mim]NTf(2) was demonstrated to correlate with both the X-ray data and the calorimetric results obtained earlier. Therefore, it was found that IR spectroscopy is able to establish the correspondence between the X-ray and the calorimetric data in this case. The joint use of X-ray diffraction, IR spectroscopy, and quantum-chemical calculations allowed us to determine the structure of all [C(2)mim]NTf(2) crystalline modifications obtained earlier by adiabatic calorimetry measurements. Thus, a new approach for the future identification of ionic liquid crystal structure by use of temperature-dependent infrared spectroscopy is suggested and justified.

Interlayer configuration of ionic liquids in a Ca-montmorillonite as evidenced by FTIR, TG-DTG, and XRD analyses

“…This could be attributed to the detachment of Cl from the CeH/Cl bonding as the interaction was between the N and the negatively charged mineral surfaces instead of Cl e . The observed bands at 656 cm À1 was caused by out-of-plane vibrations of the imidazolium ring in the cation [33]. In this study it was shifted to 727 cm À1 after adsorption/intercalation on MMT.…”

Determination of phase transition points of ionic liquids by combination of thermal analysis and conductivity measurements at very low heating and cooling rates

“…The results from three measuring cells (14 measurements; nine with simultaneous recorded conductivity, five without) were consistent and used for calculation of the mean value of T = (256.0 ± 0.4) K. This value is in good accordance with the majority of literature values (table 2). For the fourth measuring cell (eight measurements without recorded conductivity), the same crystallization points were determined as for the other measurements but for seven of the eight measurements different melting temperatures = (270.7 ± 0.1) K were obtained, independent from the applied [20,21], formation of the specific crystal structures is primarily influenced by the thermal history (cooling ? crystallization ?…”

“…If measurement errors can be disregarded, the only remaining explanation is that solid EMINTf 2 exists in at least two different crystal structures with different melting temperatures as well. According to the literature[19][20][21], [EMIM][NTf 2 ] can exist in two to four different crystalline modifications, two of them having melting temperatures comparable to the ones published in this paper [(256.0 ± 0.4) K and (270.7 ± 0.1) K]. The different modifications are mainly caused by different conformers possible for the [EMIM]-cation and [NTf 2 ]-anion and the varying energetic interactions of their combinations.…”

Carbon dioxide adsorption by zinc-functionalized ionic liquid impregnated into bio-templated mesoporous silica beads

“…The curve fitting was performed over extended regions to ensure that the deconvoluted peaks were a close fit with the overall spectrum [45]. The peaks at 741 cm -1 (blue) and 747 cm -1 (orange) correspond to the free and coordinated TFSI, respectively [17,46], and the green peaks correspond to σ SiOSi , ν SN and ν CS vibrations. The ratio of the peak area (free:coordinated) for the pure EZT3 is 9.3:1, and is 3.0:1, 3.1:1, and 3.3:1 for SALG-AT-EZT3-10, -25 and -35, respectively.…”