Abstract
A set of imidazolium-based ionic liquids (ILs), 1-(2-hydroxyethyl)-3-methylimidazolium chloride (1), 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2), and 1-butyl-2,3,4,5-tetramethylimidazolium bromide (3), has been synthesized and their structural and thermal behavior studied. Organic halides are well-known IL formers with imidazolium halides being the most prominent ones. Functionalization of the imidazolium cation by enhancing its hydrogen bonding capacity, i.e. through introduction of –OH groups or by diminishing it, i.e. through substitution of the ring hydrogen atoms by methyl groups is expected to change the inter-ionic interactions. Consequently, the solid-state structures of 1–3 have been characterized with means of single X-ray diffraction to shed light on preferential inter-ionic interactions for obtaining valuable information on anti-crystal engineering, i.e. designing ion combinations that favor a low melting point and exhibit a low tendency for crystallization. The study reveals that endowing IL forming ions with an enhanced hydrogen bonding capacity leads to a depression in melting points and kinetically hinders crystallization. This study provides hints towards new design concepts for IL design, similar to the common strategy of employing conformationally flexible ions.
1 Introduction
Ionic liquids (ILs) are nowadays receiving attention as environmentally friendly solvents [1], [2], [3] in various organic and inorganic syntheses, in which they have the ability to act not only as the solvent, but bring about additional benefits such as their ability to direct a chemical reaction [4], act as templating agents and mineralizers [5], [6], [7], [8], [9], [10], [11], [12], [13]. Their astonishing diversity of physicochemical properties [6], [7], [8], [9], [10], [11], [12], [14], [15], [16], [17], [18], [19], [20], [21], [22] like ionic conductivity, low melting points and vapor pressure, polarity, possible hydrogen bonds and thermal stability in air and water already led to a multitude of applications beyond solvents, e.g. in catalysis [4], [6], [11], [23], [24], [25], [26], [27], lubricants [28], [29], [30], [31], dye-sensitized solar cells [32], [33], [34], [35], [36], and chemical sensors [37], [38], [39]. Over the last years it has become clear, that the true advantage is the possibility to endow an IL with a desired set of properties for specific applications. Even though ILs have received tremendous attention as a new class of solvents and materials for various applications, the understanding of interactions within these liquids is still not sufficient for a rational design. It has been realized that aside from Coulombic interactions, secondary interactions such as van der Waals forces, halogen bonding, dipole–dipole, cation–π interactions as well as π–π stacking of aromatic groups are important in ILs. Understanding how these fundamental interactions at the ionic level affect the material is a prerequisite for a targeted IL design. In this respect, studying the structures of solid, crystalline ILs has shown to give important insights [40].
The family of ILs which to date has received the most attention and the widest application are imidazolium based ILs, which feature frequently a high chemical stability, electrical conductivity and have been explored for various applications, frequently as solvents for organic syntheses [41], [42], [43], [44], [45], [46], [47], [48], [49], [50], [51], [52], [53], [54], [55], [56]. Endowing such ILs with –OH functionalized cations introduces a solvation behavior comparable to traditional alcohols. Their nature in syntheses was first reported by Branco et al. [57] and further investigations were carried out regarding their use, as for example, stabilizers for the syntheses of nanoparticles [12], [58], or in Diels-Alder and enantioselective reactions. In particular, imidazolium ILs with hydroxyl groups located at the alkyl side chains of their cation not only represent an alternative for alcoholic solvents but a versatile additive in nanoparticle and peptide syntheses, or enzymatic reactions [16], [21], [27], [58], [59], [60], [61], [62], [63], [64], [65], [66], [67], [68], [69], [70], [71]. On the other hand, the Brønsted acidity of –OH group bearing IL or even of the protons of the imidazolium group alone can be detrimental for certain applications [72], [73], [74]. A commonly chosen approach is to substitute them by –CH3 groups, or use azolium cations. However, it got noted that this approach also has a significant influence on the melting point of the materials. To study how Brønsted acidic functional groups influence the properties we investigated imidazolium ILs endowed with –OH functional groups and we investigated the solid state structure of 1-(2-hydroxyethyl)-3-methylimidazolium chloride (1) and 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2). In contrast, in 1-butyl-2,3,4,5-tetramethylimidazolium bromide (3), even the acidic protons on the imidazolium head group have been substituted by alkyl groups. Additionally, the stronger Lewis base chloride is substituted for bromide, which has a lower tendency to undergo hydrogen bonds. Thus, by selectively switching on and off Brønsted acidity in ILs and studying how this affects the preferential ion–ion interactions in the solid, we aim at identifying important structure–property relations that will allow to develop guidelines for a rational IL design.
2 Experimental
Syntheses. All starting materials were commercially obtained in analytical grade and used without further purification.
1-(2-Hydroxyethyl)-3-methylimidazolium chloride (1). The synthetic procedure is a modification of the ones reported by Branco et al. [57] and Yeon et al. [75]. The starting materials 1-methylimidazole (Sigma-Aldrich, >99%; 50.00 mL, 0.627 mol) and 2-chloroethanol (Acros Organics, 99%; 50.46 mL, 0.752 mol), were mixed under cooling and refluxed at 80 °C for 24 h. After cooling to room temperature the solid precipitate was separated and then dissolved in 40.00 mL of ethanol (J. T. Baker, 99.5%) and recrystallized from cold toluene (J. T. Baker, 99.5%). Residual solvent was removed by heating at 60 °C under vacuum. Single crystals of 1-(2-hydroxyethyl)-3-methylimidazolium chloride were grown from dimethylformamide (J. T. Baker, 99.9%) under inert gas conditions.
1H NMR (250 MHz, DMSO-d6); δH/ppm: 3.72 (q, 2H), 3.88 (s, 3H), 4.24 (t, 2H), 5.45 (t, 1H), 7.74 (s, 1H), 7.78 (s, 1H), 9.26 (s, 1H); IR: υmax/cm–1: 401, 419, 436, 456, 490, 622, 652, 686, 705, 796, 870, 943, 1037, 1063, 1073, 1099, 1119, 1172, 1197, 1254, 1348, 1372, 1388, 1425, 1446, 1464, 1481, 1571, 1684, 2488, 2671, 2823, 2869, 2928, 2955, 2966, 3034, 3050, 3098, 3141. The measurements are consistent with literature data (NMR [67], IR [70], [76]).
1,3-bis-(2-Hydroxyethyl)-imidazolium chloride (2). Xiong et al. [77] synthesized 1,3-bis-(2-hydroxyethyl)-imidazolium chloride by reacting a mixture of imidazole, methanol and sodium with chloroethanol. Here, we used a different route by employing a protective group for the hydroxyl group according to Scheme 1: Imidazole (Sigma-Aldrich, 99%; 20.00 g, 0.294 mol) was mixed with sodium hydride (Sigma-Aldrich, 95%; 7.06 g, 0.294 mol) under inert gas conditions to obtain sodium imidazolide. 3,4-Dihydropyran (Acros Organics, 99%; 18.33 mL, 0.201 mol) was used in order to protect the OH functional group of 2-chloroethanol (Acros Organics, 99%; 8.99 mL, 0.134 mol) in the presence of p-toluenesulfonic acid (Merck, for analysis; 0.1154 g, 0.0007 mol). After purification by evaporation of solvents and by using chromatography with pentane/ethylacetate (9:1), respectively, of the received intermediates sodium imidazolide (3.00 g, 0.033 mol) and 2-(2-chloroethoxy)-tetrahydropyran (16.95 g, 0.103 mol) were further reacted in tetrahydrofuran (Acros Organics, 99.5%). After releasing the protective group in hydrochloric acid (J. T. Baker, 37%) the final product 1,3-bis-(2-hydroxyethyl)-imidazolium chloride was obtained via precipitation in methanolic solution as a solid.
Synthesis of 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2).
1H NMR (200 MHz, DMSO-d6); δH/ppm: 3.72 (t, 4H), 4.25 (t, 4H), 5.46 (t, 2H), 7.77 (s, 1H), 7.78 (s, 1H), 9.25 (s, 1H). The results are in agreement with literature data [77].
1-Butyl-2,3,4,5-tetramethylimidazolium bromide (3). 1-Butyl-2,3,4,5-tetramethylimidazolium bromide was synthesized by solving tetramethyl imidazole (25.50 g, 0.205 mol) and 1-bromobutane (21.85 mL, 0.274 mol) in 100 mL of toluene (J. T. Baker, 99.5%). The product was obtained by cooling after refluxing at 70 °C for 24 h.
IR: υmax/cm–1: 446, 500, 567, 581, 597, 636, 684, 740, 757, 794, 811, 836, 884, 911, 972, 994, 1031, 1053, 1079, 1119, 1133, 1155, 1196, 1225, 1246, 1268, 1322, 1353, 1374, 1404, 1428, 1446, 1485, 1532, 1646, 2761, 2870, 2929, 2954, 3005.
Single crystal X-ray structure determinations. Suitable crystals of 1–3 were selected, mounted in glass capillaries and checked for their quality on a Stoe IPDS I single crystal X-ray diffractometer (Stoe, Germany). A complete data set was measured at room temperature. Data reduction was carried out with the program package X-red [78] and numerical absorption corrections were carried out with the program X-Shape [79]. Crystal structure solution by direct methods using SHELXT [80] yielded the space group and majority of the atom positions. Subsequent difference Fourier analyses and least squares refinement with SHELXL [81] allowed for the proper assignment of the atomic positions. In the final step of the crystal structure refinements, hydrogen atoms were added and treated with the riding atom mode.
NMR spectroscopy. 1H NMR spectra were recorded on DPX-200 and DPX-250 NMR spectrometers (Bruker, Germany).
Vibrational spectroscopy. Infrared spectra (see Supplementary Material, Figure S2) were recorded with an Alpha-P spectrometer (Bruker, Germany) at room temperature in the range of 400–4000 cm–1.
Thermal analysis. Differential scanning calorimetry measurements were conducted with a DSC 204 F1 Phoenix (Netzsch, Germany) by using temperature rates of 5 °C min–1. Thermal gravimetric analysis was operated on a TGA-50 thermoanalyzer (Shimadzu, Scientific Instruments, USA) with a temperature rate of 5 °C min–1. TG-onset thermal data of the title compounds 1–3 as well as related ones are given in Table 2.
3 Results and discussion
Compounds 1–3 crystallize in the monoclinic system with the space groups P21, Cc and P21, respectively, Table 1.
Crystallographic details and refinement parameters for 1–3.
| Compound | 1 | 2 | 3 |
|---|---|---|---|
| CCDC | 1989501 | 1989502 | 1989737 |
| Chemical formula | C6H11ClN2O | C7H13ClN2O2 | C11H21BrN2 |
| Formula weight, g mol−1 | 162.62 | 192.64 | 261.21 |
| Space group, Z | P21 (no. 4), 2 | Cc (no. 9), 4 | P21/c (no. 14), 4 |
| a, Å | 7.302(2) | 17.138(9) | 9.251(1) |
| b, Å | 7.052(2) | 4.7641(9) | 8.887(1) |
| c, Å | 8.517(3) | 13.494(4) | 15.894(3) |
| β, ° | 111.13(3) | 121.56(3) | 104.75(1) |
| V, Å3 | 409.1(2) | 938.8(6) | 1263.6(4) |
| Temperature, K | 293(2) | 293(2) | 293(2) |
| Density (calculated), g cm−3 | 1.320 | 1.363 | 1.373 |
| Absorption coefficient, mm−1 | 0.404 | 0.371 | 3.222 |
| F(000) | 172 | 408 | 544 |
| θ range for data collection, ° | 2.56–24.97 | 2.79–25.00 | 2.65–25.00 |
| Index ranges | −8 < h < 8 | −20 < h < 20 | −10 < h < 10 |
| −8 < k < 8 | −5 < k < 5 | −10 < k < 10 | |
| −10 < l < 10 | −16 < l < 16 | −18 < l < 18 | |
| Intensity data collected | 2801 | 2611 | 8794 |
| Independent reflections | 1331 | 1528 | 2169 |
| Rint | 0.0223 | 0.1251 | 0.0312 |
| Completeness, % | 99.7 | 100 | 97.6 |
| Flack parameter | 0.1(1) | −0.1(2) | – |
| Data/Restraints/Parameters | 1331/1/94 | 1528/2/110 | 2169/0/135 |
| Goodness-of-fit (F2) | 1.16 | 0.65 | 0.96 |
| R1, ωR2 [I0 > 2σ(I)] | 0.0248, 0.0652 | 0.0445, 0.0917 | 0.0211, 0.0446 |
| R1, ωR2 (all data) | 0.0301, 0.0701 | 0.1095, 0.1064 | 0.0285, 0.0456 |
| Largest diff. peak and hole [e Å−3] | 0.135 and −0.150 | 0.242 and −0.255 | 0.460 and −0.242 |
The asymmetric unit for all compounds contains one formula unit. Figure 1 illustrates this, together with the observed cation–anion interactions. The observed inter-atomic distances of the imidazolium cation are in the expected region, similar to reported imidazolium halides [82], [83], [84]. The crystal structure of 1 is consistent with the previously published low temperature data [85]. The hydroxyl-ethyl side chain in 1 and 2 features a gauche conformation, induced by hydrogen bonding of the proton of the hydroxyl group(s) with chloride anions. Due to the presence of one extra H-bond donor in 2 two lone pairs of Cl− get involved in OH⋅⋅⋅Cl hydrogen bonding with the same cation (Figure 1, dO–Cl = 3.069(9) and 3.111(7) Å, ∠O–Cl–O = 122.9(2)°), while those in 1 form one OH⋅⋅⋅Cl hydrogen bond and one lp⋅⋅⋅π interaction with the imidazole ring (dO–Cl = 3.053(3) Å, dCg–Cl = 3.495(1) Å).
Fifty percent probability ellipsoid plots of basic repeating units of (a) 1, (b) 2 and (c) 3.
Additional moderate to weak [86] hydrogen bonds are present in both structures between an O(H) acceptor and one of the aromatic CH donors (Figure 2, dCH⋅⋅⋅O = 2.268(3) Å in 1 and 2.390(6) Å in 2). In spite of different number of OH⋅⋅⋅Cl hydrogen bonds additional electrostatic CH⋅⋅⋅Cl interactions are present in each structures bringing the total number of H⋅⋅⋅Cl interaction to four. These additional interactions involve two aromatic CH groups in each compound and additional CH3 group is involved in 1. All aromatic hydrogen atoms are involved in the hydrogen bonding network in 1 and 2. In addition, for 2 rather weak π–π interactions can be outlined along the crystallographic b axis (dCg–Cg = 4.764(8), slippage = 3.331 Å). These interactions are weakened not at least due to geometric restrictions created by both –C2H4OH groups. Although direct π–π stacking in 1 is not possible due to Cl−–π interactions, weak CH⋅⋅⋅π interactions have been observed between the CH3 group and the aromatic ring of the two neighboring cations (dC–C = 3.706(6), dC–H = 2.898(4) Å).
Overall packing diagram of 1 (left) and 2 (right). Crystallographic axes are color-coded for all structures: a = red, c = blue.
In summary, the crystal packing of 1 and 2 appear to be governed by similar effects, with hydrogen bonding and π⋅⋅⋅π versus and (lp)⋅⋅⋅π interactions being important. Both compounds exhibit also a comparably dense molecular packing (68.2 vs 69.6 in terms of Kitaigorodski packing index, KPI [87]).
The crystal structure of 3 having no strong H-bond donors is characterized by more delocalized Br⋅⋅⋅H bonding – each Br− anion exhibits seven connections to four different cations leading to a 3D network (Figure 3). These connections are reinforced by rather weak π–π stacking interactions (dCg–Cg = 4.77–4.85 Å, slippage = 3.18–3.42 Å) that actually involves stronger CH⋅⋅⋅π connections between the N–CH3 group and the aromatic ring of a neighboring cation. Due to the presence of longer carbon chains certain nonpolar areas can be observed along the b direction. These involve four CH3 groups two from both butyl and methyl chains, with the butyl chains featuring all-trans conformation. The butyl chains from two neighboring cations are oriented antiparallel leading to formally unpolar layers parallel to the bc plane. In fact these layers are strongly affected by Br⋅⋅⋅H bonding.
Overall packing diagram of 3.
All compounds show an appreciable thermal stability with one-step decomposition at the temperatures well above 280 °C. This behavior is well consistent with all other compounds presented in Table 2 where such data are available. Interestingly, 2 shows the highest thermal stability of the three investigated compounds, with roughly 330 °C about 40 °C higher than 1 and 3, which have about the same decomposition temperature. It appears that the extended hydrogen bonding network evoked through the additional hydroxyethyl side chain leads to a stabilization. The influence of hydrogen bonding becomes also evident when comparing the melting points. 2 shows, despite its higher molecular weight, a melting point that is about 20 °C lower than 1. 3, where no strong hydrogen bond donors and acceptors, are present shows a similar melting point to 2. However, the higher molecular weight has to be taken into account when comparing the thermal behavior.
The onset thermal data of the investigated and related compounds.
| Compound | Tg/°C | Tc/°C | Tm/°C | Td/°Ca | Ref. |
|---|---|---|---|---|---|
| 1-(2-Hydroxyethyl)-3-methyl-imidazolium chloride (1) | −46.6 | 8.4b | 83.9 | 290 | |
| 1,3-Di-(2-hydroxyethyl)-imidazolium chloride (2) | −45.5 | −3.8b | 64.4 | 329 | |
| 1-Butyl-2,3,4,5-tetramethyl-imidazolium bromide (3) | 60.5 | 288 | |||
| 1-Ethyl-3-methyl-imidazolium chloride | 14–33 | 86 | 267 | [88] | |
| 1-Ethyl-3-methyl-imidazolium bromide | 4–30 | 67 | 289 | [88] | |
| 1-Ethyl-3-methyl-imidazolium hydrosulfide | 93 | 162 | [89] | ||
| 1-Butyl-3-methyl-imidazolium chloride | −69 | 66 | 264 | [90], [91] | |
| 1-Butyl-3-methyl-imidazolium bromide | −50 | 76 | 273 | [90], [91] | |
| 1-Butyl-3-methyl-imidazolium iodide | −72 | Iolitec® | |||
| 1-Butyl-3-methyl-imidazolium hydrosulfide | 55 | 157 | [89] | ||
| 1-Dodecyl-3-methyl-imidazolium chloride | 150 | Iolitec® | |||
| 1-Dodecyl-3-methyl-imidazolium bromide | 112 | Iolitec® | |||
| 1-Dodecyl-3-methyl-imidazolium iodide | 40 | Iolitec® |
a5 °C min–1.
bCrystallization upon heating.
Another interesting observation can be made, when looking at the crystallization behavior of the studied compounds. Compounds 1 and 2 are reluctant to crystallize from the molten state and form upon cooling glasses, which devitrify upon heating and cold crystallize before melting (Figure 4).
DSC thermograms of 1–3 measured upon heating at 5 °C min–1, second heating curves.
In this context, it is also interesting to compare the obtained results with those of the widely explored 1-alkyl-3-methylimidazolium halides. For 1-ethyl-3-methyl-imidazolium halides, going from chloride [92] to bromide [93] and iodide as the counterion leads to significant changes in the molecular packing, the most obvious the destruction of π–π stacking of the imidazolium units. The hydrosulfide behaves structurally as a pseudo-halogen resulting in similar to the chloride bonding patterns and, consequently, thermal behavior. This is mirrored in the corresponding melting points (Table 2). The melting point of the bromide is lower than that of the chloride, despite its higher molecular weight. However, this trend is reversed when going to 1-butyl-3-methyl-imidazolium halides [90]. Here an interplay of increased size of the anion and cation leads to a prohibition of π–π stacking of the cations, if an efficient packing has to be assumed. However, the extension of the alkyl chain leads to an increased importance of van der Waals interactions and in the crystal structure of the bromide the butyl chains interdigitate, as it has been observed for the long chain imidazolium halides [94]. Thus, for 1-butyl-3-methyl-imidazolium halides an increase in the melting point with the heavier counter anion is observed. The increased van der Waals interactions lead as a rule to an increase in melting point from 1-ethyl-3-methyl-imidazolium to 1-butyl-3-methyl-imidazolium and further to 1-dodecyl-3-methyl-imidazolium, which is enforced by an increase in molecular weight. It is worth noting that the structural factor is though very important here as the interaction between the long carbon chains can either be maximized (in interdigitated variants) or diminished, so simple elongation of the carbon chain cannot be a determinative factor. The absence of van der Waals and π–π interactions makes 1-butyl-3-methyl-imidazolium chloride the lowest melting salt within the discussed halogenides. The corresponding hydrosulfide though exhibits even lower melting point due to hindered intermolecular H-bonding interactions. However, by endowing the cation with extensive hydrogen bonding acceptor and donor sites, leading to competition for H-bonding [95] and possible H-bonding frustration, the melting point can be even lowered further.
In summary, aside from obvious electrostatic interactions a number of weaker secondary bonding forces such as van der Waals, hydrogen bonding and π–π interactions play a decisive role in ILs, which allows to fine tune them to obtain low melting salts.
4 Conclusions
Three imidazolium-based ILs 1-(2-hydroxyethyl)-3-methylimidazolium chloride (1), 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2), and 1-butyl-2,3,4,5-tetramethy-limidazolium bromide (3) have been synthesized, followed by structural characterization and examination of their thermal properties. A comparison of their solid structures revealed significant changes in the character of intermolecular interactions and consequently their thermal behavior and stability. Both elongation of the carbon chains and OH functionalization led to the decrease of π–π interactions between the aromatic rings due to either geometric hindering or the presence of stronger OH⋅⋅⋅X (X = Cl−, HS−, Br−, I−) hydrogen bonds. Interestingly, further OH functionalization leads to decrease of the melting point due to possible H-bond frustration. Thus, endowing IL cations with strongly enhanced hydrogen bonding capacities leading to hydrogen bonding frustration which leads to a depression in the melting point as well is kinetically hampering crystallization is proposed as a concept for engineering low melting salts similar to the commonly accepted technique to increase flexibility by functionalization with conformational flexible alkyl chains.
Dedicated to Professor Dr. Ulrich Müller on the occasion of his 80th birthday.
Funding source: Royal Swedish Academy of Sciences
Award Identifier / Grant number: Unassigned
Acknowledgment
This work was supported by the Royal Swedish Academy of Sciences through the Göran Gustafsson prize in Chemistry to A.-V. M.
Author contribution: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: None declared.
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
References
1. Mallakpour, S., Dinari, M. Ionic liquids as green solvents: Progress and prospects. In Green Solvents II: Properties and Applications of Ionic Liquids, Mohammad, A., Inamuddin, D., Eds. Springer Netherlands: Dordrecht, 2012; pp. 1–32.10.1007/978-94-007-2891-2_1Search in Google Scholar
2. Antonia Pérez de los Ríos, A. I., Hollmann, F., Hernández Fernández, F. J. Ionic liquids: green solvents for chemical processing. J. Chem. 2013; https://doi.org/10.1155/2013/402172.Search in Google Scholar
3. Anastas, P. T., Stark, A. Green Solvents: Ionic Liquids, Vol. 6; Wiley-VCH: Germany, Weinheim, 2014.10.1016/B978-1-895198-82-9.50013-0Search in Google Scholar
4. Seddon, K. R. Ionic liquids for clean technology. J. Chem. Technol. Biotechnol. 1997, 68, 351; https://doi.org/10.1002/(sici)1097-4660(199704)68:4351::aid-jctb6133.0.co;2-4.10.1002/(SICI)1097-4660(199704)68:4<351::AID-JCTB613>3.0.CO;2-4Search in Google Scholar
5. Holbrey, J. D., Seddon, K. R. Ionic liquids. Clean Prod. Proc. 1999, 1, 223; https://doi.org/10.1007/s100980050036.Search in Google Scholar
6. Welton, T. Room-temperature ionic liquids. Solvents for synthesis and catalysis. Chem. Rev. 1999, 99, 2071; https://doi.org/10.1021/cr980032t.Search in Google Scholar
7. Merrigan, T. L., Bates, E. D., Dorman, S. C., Davis, J. H.Jr. New fluorous ionic liquids function as surfactants in conventional room-temperature ionic liquids. Chem. Commun. 2000, 2051; https://doi.org/10.1039/b005418f.Search in Google Scholar
8. MacFarlane, D. R., Golding, J., Forsyth, S., Forsyth, M., Deacon, G. B. Low viscosity ionic liquids based on organic salts of the dicyanamide anion. Chem. Commun. 2001, 1430; https://doi.org/10.1039/b103064g.Search in Google Scholar
9. Tokuda, H., Tsuzuki, S., Susan, M. A. B. H., Hayamizu, K., Watanabe, M. How ionic are room-temperature ionic liquids? An indicator of the physicochemical properties. J. Phys. Chem. B 2006, 110, 19593; https://doi.org/10.1021/jp064159v.Search in Google Scholar
10. Smiglak, M., Metlen, A., Rogers, R. D. The second evolution of ionic liquids: from solvents and separations to advanced materials—energetic examples from the ionic liquid cookbook. Acc. Chem. Res. 2007, 40, 1182; https://doi.org/10.1021/ar7001304.Search in Google Scholar
11. Plechkova, N. V., Seddon, K. R. Applications of ionic liquids in the chemical industry. Chem. Soc. Rev. 2008, 37, 123; https://doi.org/10.1039/b006677j.Search in Google Scholar
12. Recham, N., Chotard, J. N., Jumas, J. C., Laffont, L., Armand, M., Tarascon, J. M. Ionothermal synthesis of Li-based fluorophosphates electrodes. Chem. Mater. 2010, 22, 1142; https://doi.org/10.1021/cm9021497.Search in Google Scholar
13. Mallakpour, S., Rafiee, Z. Ionic liquids as environmentally friendly solvents in macromolecules chemistry and technology, part I. J. Polym. Environ. 2011, 19, 447; https://doi.org/10.1007/s10924-011-0287-3.Search in Google Scholar
14. Crowhurst, L., Lancaster, N. L., Pérez Arlandis, J. M., Welton, T. Manipulating solute nucleophilicity with room temperature ionic liquids. J. Am. Chem. Soc. 2004, 126, 11549; https://doi.org/10.1021/ja046757y.Search in Google Scholar PubMed
15. Davis, J. J. H. Task-specific ionic liquids. Chem. Lett. 2004, 33, 1072; https://doi.org/10.1246/cl.2004.1072.Search in Google Scholar
16. Fei, Z., Geldbach, T. J., Zhao, D., Dyson, P. J. From dysfunction to Bis-function: on the design and applications of functionalised ionic liquids. Chem. Eur. J. 2006, 12, 2122; https://doi.org/10.1002/chem.200500581.Search in Google Scholar PubMed
17. Lee, S.-G. Functionalized imidazolium salts for task-specific ionic liquids and their applications. Chem. Commun. 2006, 1049; https://doi.org/10.1039/b514140k.Search in Google Scholar PubMed
18. Weingärtner, H. Understanding ionic liquids at the molecular level: facts, problems, and controversies. Angew. Chem. Int. Ed. 2008, 47, 654; https://doi.org/10.1002/anie.200604951.Search in Google Scholar PubMed
19. França, J. M. P., Nieto de Castro, C. A., Lopes, M. M., Nunes, V. M. B. Influence of thermophysical properties of ionic liquids in chemical process design. J. Chem. Eng. Data 2009, 54, 2569; https://doi.org/10.1021/je900107t.Search in Google Scholar
20. Ficke, L. E., Novak, R. R., Brennecke, J. F. Thermodynamic and thermophysical properties of ionic liquid + water systems. J. Chem. Eng. Data 2010, 55, 4946; https://doi.org/10.1021/je100522z.Search in Google Scholar
21. Nie, N., Zheng, D., Dong, L., Li, Y. Thermodynamic properties of the water + 1-(2-hydroxylethyl)-3-methylimidazolium chloride system. J. Chem. Eng. Data 2012, 57, 3598; https://doi.org/10.1021/je3007953.Search in Google Scholar
22. Taige, M., Hilbert, D., Schubert, T. Mixtures of ionic liquids as possible electrolytes for lithium ion batteries. Z. Phys. Chem. 2012, 226, 129; https://doi.org/10.1524/zpch.2012.0161.Search in Google Scholar
23. Wasserscheid, P., Keim, W. Ionic liquids—new “solutions” for transition metal catalysis. Angew. Chem. Int. Ed. 2000, 39, 3772; https://doi.org/10.1002/1521-3773(20001103)39:213772::aid-anie37723.0.co;2-5.10.1002/1521-3773(20001103)39:21<3772::AID-ANIE3772>3.0.CO;2-5Search in Google Scholar
24. Dupont, J., de Souza, R. F., Suarez, P. A. Z. Ionic liquid (molten salt) phase organometallic catalysis. Chem. Rev. 2002, 102, 3667; https://doi.org/10.1021/cr010338r.Search in Google Scholar
25. Zhao, D., Wu, M., Kou, Y., Min, E. Ionic liquids: applications in catalysis. Catal. Today 2002, 74, 157; https://doi.org/10.1016/s0920-5861(01)00541-7.Search in Google Scholar
26. Olivier-Bourbigou, H., Magna, L., Morvan, D. Ionic liquids and catalysis: recent progress from knowledge to applications. Appl. Catal. A 2010, 373, 1; https://doi.org/10.1016/j.apcata.2009.10.008.Search in Google Scholar
27. Zhang, Q., Zhang, S., Deng, Y. Recent advances in ionic liquid catalysis. Green Chem. 2011, 13, 2619; https://doi.org/10.1039/c1gc15334j.Search in Google Scholar
28. Liu, X., Zhou, F., Liang, Y., Liu, W. Tribological performance of phosphonium based ionic liquids for an aluminum-on-steel system and opinions on lubrication mechanism. Wear 2006, 261, 1174; https://doi.org/10.1016/j.wear.2006.03.018.Search in Google Scholar
29. Sanes, J., Carrión-Vilches, F.-J., Bermúdez, M.-D. New epoxy-ionic liquid dispersions. Room temperature ionic liquid as lubricant of epoxy resin-stainless steel contacts. e-Polymers 2007, 7; https://doi.org/10.1515/epoly.2007.7.1.48.Search in Google Scholar
30. Zhou, F., Liang, Y., Liu, W. Ionic liquid lubricants: designed chemistry for engineering applications. Chem. Soc. Rev. 2009, 38, 2590; https://doi.org/10.1039/b817899m.Search in Google Scholar
31. Somers, E. A., Howlett, C. P., MacFarlane, R. D., Forsyth, M. A review of ionic liquid lubricants. Lubricants 2013, 1, 3; https://doi.org/10.3390/lubricants1010003.Search in Google Scholar
32. Wang, P., Zakeeruddin, S. M., Exnar, I., Grätzel, M. High efficiency dye-sensitized nanocrystalline solar cells based on ionic liquid polymer gel electrolyte. Chem. Commun. 2002, 2972; https://doi.org/10.1039/b209322g.Search in Google Scholar
33. Li, B., Wang, L., Kang, B., Wang, P., Qiu, Y. Review of recent progress in solid-state dye-sensitized solar cells. Sol. Energy Mater. Sol. Cells 2006, 90, 549; https://doi.org/10.1016/j.solmat.2005.04.039.Search in Google Scholar
34. Senadeera, G. K. R., Kitamura, T., Wada, Y., Yanagida, S. Enhanced photoresponses of polypyrrole on surface modified TiO2 with self-assembled monolayers. J. Photochem. Photobiol. A Chem. 2006, 184, 234; https://doi.org/10.1016/j.jphotochem.2006.04.033.Search in Google Scholar
35. Gorlov, M., Kloo, L. Ionic liquid electrolytes for dye-sensitized solar cells. Dalton Trans. 2008, 2655; https://doi.org/10.1039/b716419j.Search in Google Scholar
36. Chandra, S. Recent trends in high efficiency photo-electrochemical solar cell using dye-sensitised photo-electrodes and ionic liquid based redox electrolytes. Proc. Natl. Acad. Sci. India A 2012, 82, 5; https://doi.org/10.1007/s40010-012-0001-4.Search in Google Scholar
37. Jin, X., Yu, L., Garcia, D., Ren, R. X., Zeng, X. Ionic liquid high-temperature gas sensor array. Anal. Chem. 2006, 78, 6980; https://doi.org/10.1021/ac0608669.Search in Google Scholar
38. Oter, O., Ertekin, K., Topkaya, D., Alp, S. Emission-based optical carbon dioxide sensing with HPTS in green chemistry reagents: room-temperature ionic liquids. Anal. Bioanal. Chem. 2006, 386, 1225; https://doi.org/10.1007/s00216-006-0659-z.Search in Google Scholar
39. Tseng, M.-C., Chu, Y.-H. Chemoselective gas sensing ionic liquids. Chem. Commun. 2010, 46, 2983; https://doi.org/10.1039/b924286d.Search in Google Scholar
40. Mudring, A.-V. Solidification of ionic liquids: theory and techniques. Aust. J. Chem. 2010, 63, 544; https://doi.org/10.1071/ch10017.Search in Google Scholar
41. Schröder, U., Wadhawan, J. D., Compton, R. G., Marken, F., Suarez, P. A. Z., Consorti, C. S., de Souza, R. F., Dupont, J. Water-induced accelerated ion diffusion: voltammetric studies in 1-methyl-3-[2,6-(S)-dimethylocten-2-yl]imidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate ionic liquids. New J. Chem. 2000, 24, 1009; https://doi.org/10.1039/b007172m.Search in Google Scholar
42. Wadhawan, J. D., Schröder, U., Neudeck, A., Wilkins, S. J., Compton, R. G., Marken, F., Consorti, C. S., de Souza, R. F., Dupont, J. r. Ionic liquid modified electrodes. Unusual partitioning and diffusion effects of Fe(CN)64−/3− in droplet and thin layer deposits of 1-methyl-3-(2,6-(S)-dimethylocten-2-yl)-imidazolium tetrafluoroborate. J. Electroanal. Chem. 2000, 493, 75; https://doi.org/10.1016/s0022-0728(00)00308-9.Search in Google Scholar
43. Berger, A., de Souza, R. F., Delgado, M. R., Dupont, J. Ionic liquid-phase asymmetric catalytic hydrogenation: hydrogen concentration effects on enantioselectivity. Tetrahedron: Asymmetry 2001, 12, 1825; https://doi.org/10.1016/s0957-4166(01)00341-x.Search in Google Scholar
44. Anthony, J. L., Maginn, E. J., Brennecke, J. F. Solubilities and thermodynamic properties of gases in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate. J. Phys. Chem. B 2002, 106, 7315; https://doi.org/10.1021/jp020631a.Search in Google Scholar
45. Ding, J., Zhou, D., Spinks, G., Wallace, G., Forsyth, S., Forsyth, M., MacFarlane, D. Use of ionic liquids as electrolytes in electromechanical actuator systems based on inherently conducting polymers. Chem. Mater. 2003, 15, 2392; https://doi.org/10.1021/cm020918k.Search in Google Scholar
46. Zhang, J., Yang, C., Hou, Z., Han, B., Jiang, T., Li, X., Zhao, G., Li, Y., Liu, Z., Zhao, D., Kou, Y. Effect of dissolved CO2 on the conductivity of the ionic liquid [bmim][PF6]. New J. Chem. 2003, 27, 333; https://doi.org/10.1039/b206526f.Search in Google Scholar
47. Every, H. A., Bishop, A. G., MacFarlane, D. R., Orädd, G., Forsyth, M. Transport properties in a family of dialkylimidazolium ionic liquids. PCCP 2004, 6, 1758; https://doi.org/10.1039/b315813f.Search in Google Scholar
48. Evans, R. G., Klymenko, O. V., Price, P. D., Davies, S. G., Hardacre, C., Compton, R. G. A comparative electrochemical study of diffusion in room temperature ionic liquid solvents versus acetonitrile. Chem.Phys.Chem. 2005, 6, 526; https://doi.org/10.1002/cphc.200400549.Search in Google Scholar PubMed
49. de Souza, R. F., Padilha, J. C., Gonçalves, R. S., Rault-Berthelot, J. Dialkylimidazolium ionic liquids as electrolytes for hydrogen production from water electrolysis. Electrochem. Commun. 2006, 8, 211; https://doi.org/10.1016/j.elecom.2005.10.036.Search in Google Scholar
50. Singh, T., Kumar, A. Static dielectric constant of room temperature ionic liquids: internal pressure and cohesive energy density approach. J. Phys. Chem. B 2008, 112, 12968; https://doi.org/10.1021/jp8059618.Search in Google Scholar PubMed
51. Bowron, D. T., D’Agostino, C., Gladden, L. F., Hardacre, C., Holbrey, J. D., Lagunas, M. C., McGregor, J., Mantle, M. D., Mullan, C. L., Youngs, T. G. A. Structure and dynamics of 1-ethyl-3-methylimidazolium acetate via molecular dynamics and neutron diffraction. J. Phys. Chem. B 2010, 114, 7760; https://doi.org/10.1021/jp102180q.Search in Google Scholar PubMed
52. Mehdi, H., Binnemans, K., Van Hecke, K., Van Meervelt, L., Nockemann, P. Hydrophobic ionic liquids with strongly coordinating anions. Chem. Commun. 2010, 46, 234; https://doi.org/10.1039/b914977e.Search in Google Scholar PubMed
53. Liu, H., Maginn, E. A molecular dynamics investigation of the structural and dynamic properties of the ionic liquid 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. J. Chem. Phys. 2011, 135, 124507; https://doi.org/10.1063/1.3643124.Search in Google Scholar
54. Fakhraee, M., Zandkarimi, B., Salari, H., Gholami, M. R. Hydroxyl-functionalized 1-(2-hydroxyethyl)-3-methyl imidazolium ionic liquids: thermodynamic and structural properties using molecular dynamics simulations and ab initio calculations. J. Phys. Chem. B 2014, 118, 14410; https://doi.org/10.1021/jp5083714.Search in Google Scholar
55. Wang, G., Valldor, M., Dorn, K. V., Wilk-Kozubek, M., Smetana, V., Mudring, A.-V. Ionothermal synthesis enables access to 3D open framework manganese phosphates containing extra-large 18-ring channels. Chem. Mater. 2019, 31, 7329; https://doi.org/10.1021/acs.chemmater.9b01935.Search in Google Scholar
56. Wang, G., Valldor, M., Siebeneichler, S., Wilk-Kozubek, M., Smetana, V., Mudring, A.-V. Ionothermal synthesis, structures, and magnetism of three new open framework iron halide-phosphates. Inorg. Chem. 2019, 58, 13203; https://doi.org/10.1021/acs.inorgchem.9b02028.Search in Google Scholar
57. Branco, L. C., Rosa, J. N., Moura Ramos, J. J., Afonso, C. A. M. Preparation and characterization of new room temperature ionic liquids. Chem. Eur. J. 2002, 8, 3671; https://doi.org/10.1002/1521-3765(20020816)8:163671::aid-chem36713.0.co;2-9.10.1002/1521-3765(20020816)8:16<3671::AID-CHEM3671>3.0.CO;2-9Search in Google Scholar
58. Yang, X., Yan, N., Fei, Z., Crespo-Quesada, R. M., Laurenczy, G., Kiwi-Minsker, L., Kou, Y., Li, Y., Dyson, P. J. Biphasic hydrogenation over PVP stabilized Rh nanoparticles in hydroxyl functionalized ionic liquids. Inorg. Chem. 2008, 47, 7444; https://doi.org/10.1021/ic8009145.Search in Google Scholar
59. Holbrey, J. D., Turner, M. B., Reichert, W. M., Rogers, R. D. New ionic liquids containing an appended hydroxyl functionality from the atom-efficient, one-pot reaction of 1-methylimidazole and acid with propylene oxide. Green Chem. 2003, 5, 731; https://doi.org/10.1039/b311717k.Search in Google Scholar
60. Mi, X., Luo, S., Xu, H., Zhang, L., Cheng, J.-P. Hydroxyl ionic liquid (HIL)-immobilized quinuclidine for Baylis–Hillman catalysis: synergistic effect of ionic liquids as organocatalyst supports. Tetrahedron 2006, 62, 2537; https://doi.org/10.1016/j.tet.2005.12.045.Search in Google Scholar
61. Choi, S., Kim, K.-S., Yeon, S.-H., Cha, J.-H., Lee, H., Kim, C.-J., Yoo, I.-D. Fabrication of silver nanoparticles via self-regulated reduction by 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate. Korean J. Chem. Eng. 2007, 24, 856; https://doi.org/10.1007/s11814-007-0054-2.Search in Google Scholar
62. Ren, L., Meng, L., Lu, Q. Fabrication of octahedral gold nanostructures using an alcoholic ionic liquid. Chem. Lett. 2007, 37, 106; https://doi.org/10.1246/cl.2008.106.Search in Google Scholar
63. Sun, J., Zhang, S., Cheng, W., Ren, J. Hydroxyl-functionalized ionic liquid: a novel efficient catalyst for chemical fixation of CO2 to cyclic carbonate. Tetrahedron Lett. 2008, 49, 3588; https://doi.org/10.1016/j.tetlet.2008.04.022.Search in Google Scholar
64. Recham, N., Dupont, L., Courty, M., Djellab, K., Larcher, D., Armand, M., Tarascon, J. M. Ionothermal synthesis of tailor-made LiFePO4 powders for Li-ion battery applications. Chem. Mater. 2009, 21, 1096; https://doi.org/10.1021/cm803259x.Search in Google Scholar
65. Jalili, A. H., Mehdizadeh, A., Shokouhi, M., Sakhaeinia, H., Taghikhani, V. Solubility of CO2 in 1-(2-hydroxyethyl)-3-methylimidazolium ionic liquids with different anions. J. Chem. Thermodyn. 2010, 42, 787; https://doi.org/10.1016/j.jct.2010.02.002.Search in Google Scholar
66. Shokouhi, M., Adibi, M., Jalili, A. H., Hosseini-Jenab, M., Mehdizadeh, A. Solubility and diffusion of H2S and CO2 in the ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate. J. Chem. Eng. Data 2010, 55, 1663; https://doi.org/10.1021/je900716q.Search in Google Scholar
67. Zhang, S., Qi, X., Ma, X., Lu, L., Deng, Y. Hydroxyl ionic liquids: the differentiating effect of hydroxyl on polarity due to ionic hydrogen bonds between hydroxyl and anions. J. Phys. Chem. B 2010, 114, 3912; https://doi.org/10.1021/jp911430t.Search in Google Scholar PubMed
68. Shimizu, K., Pensado, A., Malfreyt, P., Pádua, A. A. H., Canongia Lopes, J. N. 2D or not 2D: structural and charge ordering at the solid-liquid interface of the 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ionic liquid. Faraday Discuss. 2012, 154, 155; https://doi.org/10.1039/c1fd00043h.Search in Google Scholar PubMed
69. Zhang, S., Qi, X., Ma, X., Lu, L., Zhang, Q., Deng, Y. Investigation of cation–anion interaction in 1-(2-hydroxyethyl)-3-methylimidazolium-based ion pairs by density functional theory calculations and experiments. J. Phys. Org. Chem. 2012, 25, 248; https://doi.org/10.1002/poc.1901.Search in Google Scholar
70. Hossain, M. I., El-Harbawi, M., Alitheen, N. B. M., Noaman, Y. A., Lévêque, J.-M., Yin, C.-Y. Synthesis and anti-microbial potencies of 1-(2-hydroxyethyl)-3-alkylimidazolium chloride ionic liquids: microbial viabilities at different ionic liquids concentrations. Ecotoxicol. Envriron. Saf. 2013, 87, 65; https://doi.org/10.1016/j.ecoenv.2012.09.020.Search in Google Scholar PubMed
71. Deng, F., Reeder, Z. K., Miller, K. M. 1,3-Bis(2′-hydroxyethyl)imidazolium ionic liquids: correlating structure and properties with anion hydrogen bonding ability. J. Phys. Org. Chem. 2014, 27, 2; https://doi.org/10.1002/poc.3198.Search in Google Scholar
72. Chowdhury, S., Mohan, R. S., Scott, J. L. Reactivity of ionic liquids. Tetrahedron 2007, 63, 2363; https://doi.org/10.1016/j.tet.2006.11.001.Search in Google Scholar
73. Stappert, K., Ünal, D., Mallick, B., Mudring, A.-V. New triazolium based ionic liquid crystals. J. Mat. Chem. C 2014, 2, 7976; https://doi.org/10.1039/c3tc31366b.Search in Google Scholar
74. Stappert, K., Mudring, A.-V. Triazolium based ionic liquid crystals: effect of asymmetric substitution. RSC Adv. 2015, 5, 16886; https://doi.org/10.1039/c4ra14961k.Search in Google Scholar
75. Yeon, S.-H., Kim, K.-S., Choi, S., Lee, H., Kim, H. S., Kim, H. Physical and electrochemical properties of 1-(2-hydroxyethyl)-3-methyl imidazolium and N-(2-hydroxyethyl)-N-methyl morpholinium ionic liquids. Electrochim. Acta 2005, 50, 5399; https://doi.org/10.1016/j.electacta.2005.03.020.Search in Google Scholar
76. Chaker, Y., Ilikti, H., Debdab, M., Moumene, T., Belarbi, E. H., Wadouachi, A., Abbas, O., Khelifa, B., Bresson, S. Synthesis and characterization of 1-(hydroxyethyl)-3-methylimidazolium sulfate and chloride ionic liquids. J. Mol. Struct. 2016, 1113, 182; https://doi.org/10.1016/j.molstruc.2016.02.017.Search in Google Scholar
77. Xiong, Y.-B., Wang, H., Wang, Y.-J., Wang, R.-M. Novel imidazolium-based poly(ionic liquid)s: preparation, characterization, and absorption of CO2. Polym. Adv. Technol. 2012, 23, 835; https://doi.org/10.1002/pat.1973.Search in Google Scholar
78. Provino, A., Sangeetha, N. S., Dhar, S. K., Smetana, V., Gschneidner, K. A., Pecharsky, V. K., Manfrinetti, P., Mudring, A.-V. New R3Pd5 compounds (R = Sc, Y, Gd–Lu): formation and stability, crystal structure, and antiferromagnetism. Cryst. Growth Des. 2016, 16, 6001; https://doi.org/10.1021/acs.cgd.6b01045.Search in Google Scholar
79. Nassau, K., Cherry, L. V., Wallace, W. E. Intermetallic compounds between lanthanons and transition metals of the first long period: I—preparation, existence and structural studies. J. Phys. Chem. Solids 1960, 16, 123; https://doi.org/10.1016/0022-3697(60)90082-2.Search in Google Scholar
80. Sheldrick, G. SHELXT – integrated space-group and crystal-structure determination. Acta Crystallogr. A 2015, 71, 3; https://doi.org/10.1107/s2053273314026370.Search in Google Scholar
81. Sheldrick, G. Crystal structure refinement with SHELXL. Acta Crystallogr. Sect. C: Struct. Chem. 2015, 71, 3; https://doi.org/10.1107/s2053229614024218.Search in Google Scholar PubMed PubMed Central
82. Prodius, D., Wilk-Kozubek, M., Mudring, A.-V. Synthesis, structural characterization and luminescence properties of 1-carboxymethyl-3-ethylimidazolium chloride. Acta Crystallogr. C 2018, 74, 653; https://doi.org/10.1107/s2053229618005272.Search in Google Scholar PubMed
83. Getsis, A., Mudring, A. V. Imidazolium based ionic liquid crystals: structure, photophysical and thermal behaviour of [Cnmim]Br·xH2O (n = 12, 14; x=0, 1). Cryst. Res. Technol. 2008, 43, 1187; https://doi.org/10.1002/crat.200800345.Search in Google Scholar
84. Babai, A., Mudring, A.-V. 1-Ethyl-2,3-dimethylimidazolium bromide monohydrate. Acta Crystallogr. Sect. E 2005, 61, o1534; https://doi.org/10.1107/s1600536805012948.Search in Google Scholar
85. Shanmuganathan, S., Kühl, O., Jones, P., Heinicke, J. Nickel and palladium complexes of enolatefunctionalised N-heterocyclic carbenes. Open Chem. 2010, 8, 992; https://doi.org/10.2478/s11532-010-0071-6.Search in Google Scholar
86. Steiner, T. The hydrogen bond in the solid state. Angew. Chem. Int. Ed. 2002, 41, 48; https://doi.org/10.1002/1521-3773(20020104)41:148::aid-anie483.0.co;2-u.10.1002/1521-3773(20020104)41:1<48::AID-ANIE48>3.0.CO;2-USearch in Google Scholar
87. van der Sluis, P., Spek, A. L. BYPASS: an effective method for the refinement of crystal structures containing disordered solvent regions. Acta Crystallogr. Sect. A 1990, 46, 194; https://doi.org/10.1107/s0108767389011189.Search in Google Scholar
88. Efimova, A., Pfützner, L., Schmidt, P. Thermal stability and decomposition mechanism of 1-ethyl-3-methylimidazolium halides. Thermochim. Acta 2015, 604, 129; https://doi.org/10.1016/j.tca.2015.02.001.Search in Google Scholar
89. Finger, L. H., Sundermeyer, J. Halide-free synthesis of hydrochalcogenide ionic liquids of the type [cation][HE] (E=S, Se, Te). Chem. Eur. J. 2016, 22, 4218; https://doi.org/10.1002/chem.201504577.Search in Google Scholar
90. Holbrey, J. D., Reichert, W. M., Nieuwenhuyzen, M., Johnson, S., Seddon, K. R., Rogers, R. D. Crystal polymorphism in 1-butyl-3-methylimidazolium halides: supporting ionic liquid formation by inhibition of crystallization. Chem. Commun. 2003, 1636; https://doi.org/10.1039/b304543a.Search in Google Scholar
91. Fredlake, C. P., Crosthwaite, J. M., Hert, D. G., Aki, S. N. V. K., Brennecke, J. F. Thermophysical properties of imidazolium-based ionic liquids. J. Chem. Eng. Data 2004, 49, 954; https://doi.org/10.1021/je034261a.Search in Google Scholar
92. Dymek, C. J., Grossie, D. A., Fratini, A. V., Wade Adams, W. Evidence for the presence of hydrogen-bonded ion-ion interactions in the molten salt precursor, 1-methyl-3-ethylimidazolium chloride. J. Mol. Struct. 1989, 213, 25; https://doi.org/10.1016/0022-2860(89)85103-8.Search in Google Scholar
93. Elaiwi, A., Hitchcock, P. B., Seddon, K. R., Srinivasan, N., Tan, Y.-M., Welton, T., Zora, J. A. Hydrogen bonding in imidazolium salts and its implications for ambient-temperature halogenoaluminate(III) ionic liquids. J. Chem. Soc. Dalton Trans. 1995, 3467; https://doi.org/10.1039/dt9950003467.Search in Google Scholar
94. Yang, M., Mallick, B., Mudring, A.-V. On the mesophase formation of 1,3-dialkylimidazolium ionic liquids. Cryst. Growth Des. 2013, 13, 3068; https://doi.org/10.1021/cg4004593.Search in Google Scholar
95. Hunt, P. A., Ashworth, C. R., Matthews, R. P. Hydrogen bonding in ionic liquids. Chem. Soc. Rev. 2015, 44, 1257; https://doi.org/10.1039/c4cs00278d.Search in Google Scholar PubMed
Supplementary Material
The online version of this article offers supplementary material (https://doi.org/10.1515/zkri-2020-0046).
© 2020 Kai Richter et al., published by De Gruyter, Berlin/Boston
This work is licensed under the Creative Commons Attribution 4.0 International License.
