Perspective pubs.acs.org/JPCL
Mesoscopic Structural Heterogeneities in Room-Temperature Ionic Liquids Olga Russina,*,† Alessandro Triolo,*,‡ Lorenzo Gontrani,‡ and Ruggero Caminiti† †
Dipartimento di Chimica, Università di Roma, ‘La Sapienza’, P. le Aldo Moro 5, I-00185 Roma, Italy Istituto di Struttura della Materia Consiglio Nazionale delle Ricerche, Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy
‡
ABSTRACT: Ionic liquids represent an exciting novel class of materials with potentially enormous applicative impact; they are proposed as environmentally responsible replacements for the noxious volatile organic solvents, as smart separation and catalysis media, or to develop electrochemical devices, just to mention a few examples. Recently, compelling experimental as well as computational evidence highlighted the complexity of RTIL morphology at the mesoscopic spatial scale, as compared to traditional molecular liquids. In this Perspective, we report on our current understanding on the nature of structural heterogeneities in ionic liquids, describing new experimental data supporting a microphase segregation structural model for these systems and proposing topics for further study.
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upon increasing the alkyl chain length,13 their complex solvation dynamics,11,14 and so forth.
oom-temperature ionic liquids (RTILs) are organic compounds that are composed solely of ionic species and show a low (if any) melting point, below 100 °C. The interest for these materials stems from several smart properties, including negligible vapor pressure, wide liquid range, and high thermal and electrochemical stability. They are presently finding application in several fields such as electrochemistry, (bio)catalysis, separation, synthesis, and so forth.1−5 It is very well-known the possibility of modulating RTIL’s bulk properties by applying minor changes to their chemical architecture. This led to the terminology of designer solvents.6 Typical RTILs, such as 1-alkyl-3-methylimidazolium tetrafluoroborate, are characterized by a polar head (e.g., imidazolium, pyridinium, piperidinium, ammonium, and phosphonium) bearing a positive charge and an alkyl tail (very often moieties ranging from methyl to dodecyl lead to ionic compounds that remain liquid at ambient temperature) and an anion, such as BF4−, PF6−, Cl−, N((SO2)CF3)2− (hereinafter indicated as Tf2N), and so forth. RTILs that are characterized by the alkyl chain linked to the anion have been proposed as well (e.g., alkylsulfate ones). RTILs are characterized by a distinct degree of mesoscopic order: this represents one of their most peculiar properties. As a matter of fact, structural heterogeneities occur over a spatial scale of a few nanometers, and the evidence so far collected indicates that this is the consequence of the segregation of the alkyl tails into mesoscopic domains. Such an organization7−12 might be responsible for several of the RTILs’ peculiar properties, including their ability to dissolve both polar and apolar compounds (that might then distribute into different portions of the structurally heterogeneous RTIL morphology), the anomalous trend observed for the viscosity © 2011 American Chemical Society
RTILs are characterized by a distinct degree of mesoscopic order: this represents one of their most peculiar properties. As a matter of fact, structural heterogeneities occur over a spatial scale of a few nanometers, and the evidence so far collected indicates that this is the consequence of the segregation of the alkyl tails into mesoscopic domains.
The first proposal for the existence of cluster entities or aggregates in bulk RTILs was done on the basis of viscosity and conductivity measurements on a family of [Cnmim][Tf2N] Received: October 1, 2011 Accepted: December 2, 2011 Published: December 2, 2011 27
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salts by Watanabe and co-workers.15 In the same period, Hamaguchi and co-workers reported their Raman spectroscopy data on a series of [Cnmim][BF4] and [Cnmim][Cl] salts, proposing that these materials might be characterized by a local ordering or structures smaller than ∼100 Å.16 This indirect evidence of clustering in neat RTILs (that might be partially accounted for in terms of dynamic, rather than structural, heterogeneities) was supported shortly after by a series of molecular dynamics simulations from independent groups. Ribeiro et al. used united-atom MD simulations to extract the diffraction pattern from a series of alkylimidazolium salts and evidenced the existence of a low-Q peak.17 Using a coarsegrained MD approach, Voth et al., proposed the segregation of alkyl chains in nanodomains.18 Canongia Lopes and Padua later used fully atomistic MD simulations to provide what is now considered to be sound computational evidence of the existence of nanoscale segregated morphology in RTILs and highlighted that the charged moieties tend to interconnect into a three-dimensional network, where the segregated alkyl domains are embedded.19 In 2007, the first experimental evidence of the existence of a well-defined spatial scale associated with the long-range order in bulk RTILs was provided on the basis of small−wide-angle X-ray scattering (SWAXS) by some of us.20 This technique allows probing of electron density fluctuations over a spatial scale from Angstroms to several nanometers; thus, it is an ideal probe to probe RTILs’ complex morphology. In those measurements, the existence of a low-momentum-transfer amorphous halo (hereinafter indicated as low-Q peak) was highlighted, and its dependence upon the RTIL’s alkyl chain length was shown. Since then, several other RTILs have been found to be characterized by such a feature that reflects the establishment of structural periodicities in bulk RTILs. Imidazolium-based RTILs represent the most explored family in this respect; for example, systematic studies have been presented by varying the anion20−22 and comparing asymmetric/ symmetric cations.23,24 Since the first computational evidence and, later, the experimental diffraction ones, it was proposed that the mentioned features are related to a specific nanoscale segregation behavior that occurs as a consequence of the nature of the interactions experienced by the different moieties of the RTIL molecules, namely, Coulombic interactions between the charged portions (e.g., the cation polar head and the anion) and dispersive ones between the alkyl tails. The substantially different spatial extent and strength of these two kinds of interactions would lead to the segregation of the alkyl chains into a domain-like morphology that develops in the framework determined by the strongly interacting charged moieties. Recently, this complex scenario has been questioned on the basis of neutron scattering experiments and computational studies by the work of the Hardacre’s and Margulis’s groups.25,26 On the basis of small-angle neutron scattering measurements done on a series of selectively deuterated [Cnmim][PF6] salts (alkyl = butyl, hexyl, octyl), Hardacre and co-workers observed that the low-Q peak emerges as a consequence of the contribution of the imidazolium head and is not related to the scattering from the alkyl tails.25 Together with this, they proposed that the linear trend observed for the nanoheterogeneity’s characteristic spatial scale versus n20,21,27 is part of a more complex trend including both shorter-chain
(cation−cation separation) and longer-chain (cation−cation interlayer spacing of liquid-crystalline phases) members, and as such, it can be accounted for in a model that requires only physical elongation of the cation and does not require clustering or nanoscale structuring to generate the observed features. The proposed minimalist mechanism that is supported by Margulis’s simulations26 then invokes the geometrical anisotropy of the chemical architecture in this specific class of RTILs that leads first-neighbor cations (that mostly contribute to the scattering) being separated by the alkyl tails, thus introducing the n-related dependence of the low-Q peak position. Hardacre’s scenario was recently supported by the simulation study from Margulis and co-workers, who described the morphology of a series of imidazolium-based RTILs (namely, [C6mim][Cl], [C8mim][PF6], and [C10mim][PF6]).26 These authors observed strong analogies between the low-Q portion of the diffraction pattern from the crystalline phases and the liquid ones. These analogies led them to propose that there are strong resemblances in the morphologies of the two phases, and accordingly, the low-Q peak in the liquid phase is strongly related to the typical distance between charged groups separated by the long cationic alkyl tails in the crystalline phase, thus merely reflecting the intrinsic anisotropy of the cation. Two kinds of nearest neighbors are possible, those in which close contact between polar groups are sterically allowed and those that because of cationic anisotropy (the alkyl tails) are separated by a typical longer length scale associated with the alkyl tail. So far, no conclusive rationalization could be provided for this experimental evidence, and for this reason, new studies, both experimental and computational, will be required. One of the issues that is presently attracting attention is the temperature dependence of this structural feature. While low-Q Bragg peaks due to crystalline phases in ILs tend to shift with increasing temperature toward lower-Q values (in agreement with the density’s temperature dependence), the low-Q peak related to the isotropic liquid state shifts toward higher Q values with increasing temperature. We reported this trend in our first paper dealing with the low-Q peak in ILs,20 and more recently, as temperature-resolved studies become more and more common in this field, other researchers reported on the temperature dependence of the IL's diffraction pattern. For example, Castner and co-workers recently reported small-angle X-ray scattering (SAXS) data for both a series of pyrrolidiniumbased salts with alkyl chains with n = 4, 6, 8, and 10 and for a phosphonium salt;28,29 in these studies, however, the temperature dependence of the low-Q peak was not monitored in detail. Saboungi and co-workers reported the temperature dependence of the low Q peak in [C6mim][Br].30 In the inset of Figure 1, we show the results from our SWAXS study on [C10mim][Br] as a function of temperature (between −100 and 150 °C); the low-Q peak can be very well detected over the whole probed temperature range. It can be appreciated that, upon increasing the temperature, it gets wider and shifts toward higher Q values. Furthermore, it is noteworthy that even at the highest temperature reached in this data set (that is the highest ever reached in SWAXS studies on RTILs), the low-Q peak still exists, thus indicating that the structural heterogeneities are still present at a temperature as high as 150 °C. Using a coarse-grained MD approach, Voth and co-workers observed that at high enough temperature, the segregation of the alkyl tails gets progressively weaker, and eventually, the domains are virtually molten.31 So far, 28
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Figure 1. (inset) SWAXS diffraction patterns from [C10mim][Br], as a function of temperature, between −100 °C and 150 °C. (main) Temperature dependence of the low-Q peak position for [C10mim][Br] (blue squares) and [C6mim][Br] (red circles).30
Figure 2. SWAXS diffraction patterns from 1-heptyl-3-methylimidazolium Tf2N (C7mimTf2N) and 1-methyl-1-heptylpiperidinium Tf2N (PIP17Tf2N) at ambient temperature.
no experimental evidence of such a melting phenomenon could be achieved, and we report here that at temperatures as high as 150 °C, the diffraction signature of the existence of mesoscopic structural heterogeneities is still present. The T dependence of the low-Q peak position for [C10mim][Br] is reported in Figure 1 and is compared with the corresponding quantity reported for [C6mim][Br] by Saboungi and co-workers.30 It can be noticed that when probed over a large temperature range, the T dependence of the low-Q peak position is quite complex. Above approximately 50 °C, both [C6mim][Br] and [C10mim][Br] show an almost linear trend; however, in the case of [C10mim][Br], where a large temperature range is available, it emerges that this linear trend is lost below 50 °C, and only below ∼−50 °C is an essentially T independent regime reached, consistently with a glass transition estimated to be ∼230 K (−40 °C). Of course, a detailed understanding of mesoscopic order in ILs will require accounting also for this complex phenomenology. The existence of structural heterogeneities represents a feature that is common not only to imidazolium-based ILs but also to other classes of RTILs, including piperidinium-,32 phosphonium-,29,33 and ammonium-based34,35 salts. The latter nonaromatic cations are also characterized by diffraction peaks at low Q. However, differences seem to exist between aromatic (e.g., imidazolium) and nonaromatic ILs, from this point of view. We recently explored piperidinium-based ILs with side alkyl chains ranging from ethyl to heptyl and highlighted that these salts are characterized by a low-Q peak position that is distinctly higher than the corresponding position found in imidazolium-based ILs32 (see Figure 2 for the case of the heptyl side chain). This implies that the heterogeneity’s characteristic size, D, is distinctly smaller in nonaromatic ILs than that in aromatic ones. Moreover, the observed slope of D versus n is found to be different in aromatic (∂D/∂n)imidazolium > 2.0 Å/CH2 unit) and nonaromatic ILs (∂D/∂n)piperidinium = 1.1 Å/CH2 unit) (Figure 3). Recently, Castner and co-workers reported a slope of (∂D/∂n)pyrrolidinium = 1.8 Å/CH2 unit for a family of nonaromatic pyrrolidinium-based ILs.28 Accordingly, values for such a parameter that are distinctly below 2 seem to characterize nonaromatic ILs, while we invariably detected (∂D/∂n)imidazolium ≥ 2.0 Å/CH2 unit for this class of aromatic ILs. At the present stage, the reasons for such differences between aromatic and
Figure 3. Side alkyl chain length dependence of the structural heterogeneities for the families of 1-alkyl-3-methylimidazolium Tf2N and 1-alkyl-1-methylpiperidinium Tf2N, at ambient temperature.
nonaromatic ILs (the latter being characterized by smaller values for both D and (∂D/∂n)) are not clear yet. Protic ionic liquids36,37 (PILs) (an interesting class of nonaromatic ILs that can develop extensive H-bonding networks across the bulk liquid, thus introducing additional structural correlations) have also been shown to be characterized by long-range order, similarly to the other RTILs. Atkin and coworkers reported the existence of a low-Q peak in EAN and PAN (ethyl- and propylammonium nitrate, respectively).38 These results are interesting as, so far, no indication of the existence of a low-Q peak was reported for ILs with such short alkyl chains, namely, ethyl and propyl (we notice that we identified the occurrence of a low-Q peak for chains longer than butyl and, in the present report, of propyl imidazolium salts, vide infra). These authors propose, on the basis of the empirical potential structural refinement (EPSR) description of neutron diffraction data, that the nanostructure is generated by electrostatic and H-bonding interactions between ions that drive the segregation of the nonpolar alkyl chains.39 In the same context, Drummond and co-workers published a series of papers related to the occurrence of the low-Q peak in a series of neat PILs and their binary mixtures.40,41 They showed that neat PILs are characterized by a very similar long-range order as the one described so far for imidazolium-based RTILs. Moreover, 29
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range is even lower than the one observed for the 1-ethyl-3methyl imidazolium salt! This result together with recent similar findings from the groups of Atkin, Drummond, Castner, and ours indicates that the increased polarity of side chains due to the presence of chemical units such as hydroxyl or ether groups has the overall effect of disrupting (or partially doing so) the mesoscopic order that is otherwise found when the side chain is an apolar alkyl one. Of course, these observations should also be interpreted considering that the ether portions along the chain are not only more flexible than alkyl chains but that they can also preferentially interact with the imidazolium group though either intra- or intermolecular H-bonding. The latter effect, however, is, in our view, a mere consequence of the increased polarity along the side chain that introduces an enhanced tendency to interact with other polar/charged moieties with respect to the apolar alkyl chain. In this respect, then, we describe the structure in alkyl chain bearing ILs in terms of a morphological organization driven by the charged portions, where the side-chain moieties simply tend to segregate in nanometer-scale domains, as long as their polarity does not allow interactions with the charged moieties. Of course, this hypothesis will require further validation tests; right now, we are preparing a series of RTILs characterized by side chains with methylene units replaced by oxygen atoms or with terminal methoxy groups, where these proposals will be tested.
in their study on PILs and their precursor Bronsted acids and bases (e.g., pentylammonium nitrate (PeAN), nitric acid, and pentylammine, respectively), they observed that, while PILs are characterized by the above-mentioned structural correlations in the nanometer-spatial scale, both HNO3 and pentylammine are featureless in the same Q range.42 Both the Atkin’s and Drummond’s groups (and more recently Castner’s and our groups) identified the role played by the chain’s polarity to determine the occurrence of the nanosegregation. Atkin observed that while EAN shows a low-Q peak, ethanol−ammonium NO3 (EtANO3) shows only a minor feature in the same Q range.39 Similarly, Drummond showed in a wider sample set that alkanolammonium-based PILs do not show appreciable low-Q features at odd with the behavior shown by their corresponding alkylammonium counterparts.40 We recently have shown that the replacement of an hexyl chain with an essentially isoelectronic ether-like chain, such as methoxyethoxymethyl (CH 3 −O−CH 2 −CH 2 −O−CH 2 −), leads to the disappearance of the low-Q peak.7 In Figure 4,
The increased polarity of side chains due to the presence of chemical units such as hydroxyl or ether groups has the overall effect of disrupting (or partially doing so) the mesoscopic order that is otherwise found when the side chain is an apolar alkyl one.
Figure 4. SWAXS diffraction patterns from the series 1-alkyl-3methylimidazolium tetrafluoroborate ([Cnmim][BF4]), with n = 2, 3, 4, 6, and 8, and 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate [C2OHmim][BF4], at ambient temperature.
we show a related example of the role played by the presence of oxygen atoms along the tail chain (and hence by the introduction of polarity in the side tail, as compared to the alkyl one). In particular, 1-alkyl-3-methylimidazolium BF4 diffraction patterns are shown for alkyl chains with n = 2, 3, 4, 6, and 8, together with the one from 1-(2-hydroxyethyl)-3methylimidazolium tetrafluoroborate ([C2OHmim][BF4]), where the side chain is − CH2−CH2−OH. Limiting our attention to the series of 1-alkyl-3-methyl imidazolium salts, we notice first that this is the first example where an alkyl chain as short as propyl is found to show some excess scattering (that can be fitted with a peak) with respect to the scattering pattern from [C2mim][BF4] and, accordingly, to induce the occurrence of the low-Q peak. So far, experimental evidence has been found that 1-alkyl-3-methyl imidazolium was characterized by the presence of a low-Q peak only for alkyl ≥ butyl. As a further observation, we find noteworthy the absence of excess scattering (with respect to the diffraction pattern from [C2mim][BF4]) in the Q range of 0 ≤ Q(nm−1) ≤ 10 in the diffraction pattern from [C2OHmim][BF4]. As a matter of fact, the scattering intensity for this sample in the mentioned Q
Another increasingly explored topic is the effect of addition of different (either polar or apolar) compounds to RTILs on their mesoscopic morphology. The complex and heterogeneous morphology in neat RTILs is envisaged to be responsible for their enhanced solubility properties toward several compounds that can be hosted in the segregated structure. In fact, due to the existence of structural heterogeneities in neat RTILs, the distribution of solutes in these solvents is far from being homogeneous; depending on their polarity, the solutes tend to segregate into the structural domains for which they have larger affinity. For example, apolar compounds (e.g., n-hexane) will distribute into the nonpolar domains, avoiding interactions with charged groups; on the other hand, polar molecules, such as water, will reside in the charged network, developing extensive hydrogen bonding interactions with the charged moieties. When added to neat RTILs, the additives are not simply hosted but may play a role in affecting the morphology of the 30
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resulting mixture as well. It can be expected that a detailed exploration of these issues will turn out to be of high importance for understanding and improving the performances of these binary systems. After the computational study from Canongia Lopes and Padua,43 who explored the privileged distribution of polar compounds in the charged portion of the segregated morphology and of apolar compounds in the alkyl tails domains, interesting experimental results have been presented based on spectroscopic and diffraction techniques. For example, Quitevis and co-workers explored the selective distribution of CS2 into the alkyl tail domains of [C5mim][Tf2N] using Kerr spectroscopy. Their study allowed one to assess that CS2, when dispersed into the RTIL, is characterized by a vibrational spectrum resembling its own when dissolved in pure pentane.44 Figure 5. SWAXS diffraction patterns from neat 1-decyl-3methylimidazolium chloride ([C10mim][Cl]), decanol (C10−OH), and their binary mixtures containing 70, 87, and 94 mol % in decanol, at ambient temperature. (inset) Low-Q peak position for the abovementioned samples as a function of decanol content, at ambient temperature.
Due to the existence of structural heterogeneities in neat RTILs, the distribution of solutes in these solvents is far from being homogeneous; depending on their polarity, the solutes tend to segregate into the structural domains for which they have larger affinity.
increasing alcohol content; accordingly, the RTIL addition to the structured alcohol strongly affects its mesoscopic order, leading to a large increase of the nanosegregated domain size (that is proportional to the inverse of the low-Q peak position). An appropriate modeling of these structural features, presumably based on computational methods, is envisaged to be fundamental in order to better describe and optimize bulkstate performances of these technologically important mixtures. When hexane, a representative apolar compound, is added to PILs in the limited concentration range that is experimentally accessible due to solubility limits, only minor changes are observed in the low-Q peak position with increasing hexane content.40 On the other hand, aprotic ILs seem to behave differently. In Figure 6, we show SWAXS data from different
Another pertinent study from Drummond and co-workers described SWAXS patterns from mixtures of PILS with different compounds, namely, water, alcohols, and hexane.40 Their study showed that the structurally heterogeneous morphology that characterizes neat PILs is maintained upon water addition as the latter compound gets localized into the charged region and has little effect on the apolar domains, thus leading to small changes in their size. They also described the effect played by short-chained linear alcohols (from ethanol to butanol) by showing that when there is a strong difference in the size of structural heterogeneities originating from neat alcohols and PILS (e.g., when PeAN is considered), the low-Q peak position of the corresponding binary mixtures changes in a continuous way; on the other hand, a more complex behavior is observed when alcohols are added to short-chained PILs (such as EAN). These observations seem to be valid also for the case of RTIL− alcohol mixtures (i.e., when the RTIL is not a PIL); in Figure 5, we show SWAXS data from [C10mim][Cl]/decanol mixtures, and in the inset, the concentration dependence of the low-Q peak position is reported. It emerges that the imidazoliumbased RTIL, when mixed with decanol, behaves very similarly to what is found for PIL/alcohol systems, such as PeAN/ R−OH (where R = ethyl, propyl, and butyl). These data can be rationalized proposing that, in the IL-rich range, the alkyl chain originating from the alcohol distributes inside of the RTIL’s alkyl domains and interactions between the charged moiety and the hydroxyl units occur; such an organization however only marginally affects the mesoscopic organization of the neat RTIL. On the other hand, in the alcohol-rich range, the low-Q peak position shifts to higher values in a very steep way upon
Figure 6. SWAXS diffraction patterns from neat 1-octyl-3-methylimidazolium tetrafluoroborate ([C8mim][BF4]) and its binary mixtures with n-hexane, containing 3, 6, 9, and 15 mol % in n-hexane, at ambient temperature. (inset) Comparison between the low-Q peak position dependence on n-hexane content for the above-mentioned samples and for pentylammonium nitrate (PeAN)/n-hexane mixtures (after ref 40), at ambient temperature.
[C8mim][BF4] and hexane mixtures, while in the inset, we show a comparison between the hexane content dependence of 31
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the low-Q peak positions for PeAN/hexane40 and [C8mim][BF4]/hexane mixtures; it can be appreciated that in the latter case, a large shift of the low-Q peak position occurs, opposite to the trend observed for PeAN/hexane mixtures. This difference might reflect the strong H-bonding capability of PILs; when additives that do not interfere with H-bonding (such as hexane) are added to PILs, they simply get hosted in the rigid framework that is built up by the H-bonding-mediated network, without introducing appreciable structural deformation with respect to the neat PIL morphology. On the other hand, changes in the mesoscopic organization are found when the same apolar compound is added to less (H-bonding)-structured RTILs. In conclusion, we reported on some examples of the complexity of mesoscopic spatial organization in RTILs. While much progress have been made in describing several features of this phenomenon, both experimentally and computationally, we stress that much is still to be understood on this puzzling topic. So far, large efforts have been paid in describing mesoscopic order in neat materials, exploring the role played by variables such as anion nature, symmetry of the cation’s head, aromatic versus nonaromatic cations, and alkyl versus polar side chains. Our recent data, together with recent literature data, prompt us to apply future efforts to the investigation of binary mixtures of RTILs with different compounds, such as other RTILs and polar and apolar compounds. Moreover, the role of external parameters such as temperature, hydrostatic pressure (both positive and negative), and magnetic fields should be investigated in order to better understand how morphology is affected by extreme conditions. We also stress that so far, only limited efforts have been paid to exploring the dynamical consequences of such a structural complexity, and spatially resolved techniques such as quasielastic neutron45,46 as well as inelastic X-ray scattering are envisaged to play a major role in this direction. Finally, we stress that the synergistic use of both computational and experimental techniques will be a powerful tool to access a deeper understanding of the mentioned structural complexity in ionic liquids and their mixtures.
Biographies Olga Russina graduated in Physics from Astana State University (Kazakhstan) and obtained her Ph.D. in Physics at the Technical University in Berlin. She focused on ionic liquids during a Post-Doc at HMIBerlin, reporting on nanosegregation in ILs. She is now Research Associate at “Sapienza” University of Rome, studying structural/dynamic properties of ILs, using computational and experimental techniques. Alessandro Triolo graduated in Chemistry from the University of Palermo, where he also received a Ph.D. in Physical Chemistry (1998). After serving as Research Associate at Heriot-Watt University and the NSE instrument at the Berlin Reactor, he is now Researcher at the Istituto Struttura Materia CNR. He is presently coordinating a multidisciplinary research program on structural/dynamic properties of ILs and their mixtures with molecular and macromolecular compounds, exploiting the synergic complementarity between X-ray/ neutron scattering-based techniques and computational ones. Lorenzo Gontrani (1974) received a Chemistry degree Sapienza” University of Rome (Italy) in 1998 and a Theoretical Chemistry from Pisa University in 2002. postdoctoral studies in computer programming and simulations, he is now Research Associate at ISM-CNR. author of 23 publications in computational chemistry.
Ruggero Caminiti graduated in Chemistry from Rome “La Sapienza” in 1974. After serving as Researcher and Professor at Cagliari University, he is currently Full Professor of Physical Chemistry at “La Sapienza” University of Rome and studies the structural properties of noncrystalline materials with energy dispersive X-ray diffraction. He has authored more than 210 publications in the field.
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ACKNOWLEDGMENTS We acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities and would like to thank Dr. M. F. Martinez, T. Narayanan, and M. Di Michiel for their kind and competent assistance in using beamlines ID02 and ID15B. We acknowledge financial support from the following sources: FIRB “Futuro in Ricerca” (RBFR086BOQ _001), PRIN2009 (2009WHPHRH_003), and Progetto Ateneo 2010 from “Sapienza” University of Rome. Useful discussions with Prof. H.-o Hamaguchi, E. W. Castner, and H. Shirota are acknowledged.
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The synergistic use of both computational and experimental techniques will be a powerful tool to access a deeper understanding of the mentioned structural complexity in ionic liquids and their mixtures.
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from “La Ph.D. in After his molecular He is the
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