Rotational correlation times, diffusion coefficients and quadrupolar peaks of the protic ionic liquid ethylammonium nitrate by means of 1H fast field cycling NMR relaxometry

Overbeck, Viviane; Appelhagen, Andreas; Rößler, Ronja; Niemann, Thomas; Ludwig, Ralf

doi:10.1016/j.molliq.2020.114983

Cited by 17 publications

(29 citation statements)

References 91 publications

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“…Intensity decay in neat ILs is typically non-exponential [24,35,51,53,55], and the scope and complexity of interactions in neat ILs has been shown to require up to five exponentials to fully and adequately describe the intensity decay data [55]. Reports have suggested that ion translational/diffusional motions are collectively described by sub-picosecond dynamics and slower solvent dynamics [18,20,40,41,43,47]. Samanta described additional contributions to solute-solvent interactions, such as solvent shell reorganization, orientational relaxation, dipolar interactions, aggregate translation and rotation, etc., that will also influence the C153 emission [35].…”

Section: Time-resolved Spectroscopymentioning

confidence: 99%

“…In other work, Maroncelli's group showed that the C153 solvation times in several IL classes (imidazolium, ammonium, and phosphonium) follows a well-defined linear correlation with viscosity that was a linear extension of that observed in conventional dipolar solvents [24,25]. To date, the role that IL-IL and/or IL + cosolvent interactions play in modified IL solutions remains a topic interest [2,7,15,16,18,[40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 98%

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Coumarin 153 Dynamics in Ethylammonium Nitrate: The Effects of Dilution with Methanol

Heitz

Sabo

Robillard

2021

Sustainable Chemistry

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Magic angle intensity decay and dynamic fluorescence anisotropy measurements were made on the binary solvent system composed of ethylammonium nitrate ([N2,0,0,0+][NO3−], EAN) + methanol (MeOH) across the complete EAN mole fraction range (xIL = 0–1) using the neutral dipolar solute coumarin 153 (C153) at 295 K. Stokes–Einstein–Debye (SED) hydrodynamic theory was used as a model framework to assess the C153 rotational reorientation dynamics. Departure from stick SED prediction was observed (in contrast to literature reports that used cationic or anionic dyes) and indicated a significant influence of domain nanoheterogeneity on probe dynamics. Steady-state spectroscopy indicated minimal changes in spectral peak and width with mole fraction, except at xIL = 0.3 where absorption widths decreased by ~170 cm−1, signaling that C153 sensed a change in solution heterogeneity. Magic angle intensity decays corroborated the steady-state observation and the excited-state lifetimes showed a marked change from xIL = 0.2–0.4 where EAN-EAN interactions became notably more significant. C153 average rotation times (⟨τrot⟩) showed significant solvent decoupling with increased EAN. The rotational data were fit to a power law dependence, ⟨τrot⟩ ∝ (ηT)p, where p = 0.82, demonstrating the presence of dynamic heterogeneity in the EAN/MeOH solutions. With increased EAN, rotation times showed that the heterogeneity became increasingly more significant since the rotation times systematically decreased away from the hydrodynamic stick limit.

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Section: Time-resolved Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Coumarin 153 Dynamics in Ethylammonium Nitrate: The Effects of Dilution with Methanol

Heitz

Sabo

Robillard

2021

Sustainable Chemistry

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“… 14 Thus, the application of FFC to ionic liquids can provide unique insights regarding rotational and translational dynamics. 15 − 18 …”

Section: Introductionmentioning

confidence: 99%

“…For instance, FFC experiments can be used to probe rotational and translational movements simultaneously, − thereby providing additional information that cannot be obtained using pulse-field gradient NMR, which measures translational motion . Thus, the application of FFC to ionic liquids can provide unique insights regarding rotational and translational dynamics. − …”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics of Ionic Liquids from Fast-Field Cycling NMR and Molecular Dynamics Simulations

et al. 2022

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Understanding the connection between the molecular structure of ionic liquids and their properties is of paramount importance for practical applications. However, this connection can only be established if a broad range of physicochemical properties on different length and time scales is already available. Even then, the interpretation of the results often remains ambiguous due to the natural limits of experimental approaches. Here we use fast-field cycling (FFC) to access both translational and rotational dynamics of ionic liquids. These combined with a comprehensive physicochemical characterization and MD simulations provide a toolkit to give insight into the mechanisms of molecular mechanics. The FFC results are consistent with the computer simulation and conventional physicochemical approaches. We show that curling of the side chains around the positively charged cationic core is essential for the properties of ether-functionalized ionic liquids, and we demonstrate that neither geometry nor polarity alone are sufficient to explain the macroscopic properties.

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“…We will show that for the case of hydroxyl-functionalized ILs, essentially four different HB lifetimes have to be considered, each valid in its own right, and each associated with different aspects of HB breaking and HB reformation. Short-time kinetics can be probed by ultrashort laser spectroscopy, − whereas the long-time behavior falls in the realm of NMR relaxation techniques. − …”

Section: Introductionmentioning

confidence: 99%

Hydrogen Bonds between Ions of Opposite and Like Charge in Hydroxyl-Functionalized Ionic Liquids: an Exhaustive Examination of the Interplay between Global and Local Motions and Intermolecular Hydrogen Bond Lifetimes and Kinetics

2021

Self Cite

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Hydroxyl-functionalized ionic liquids (ILs) represent a new interesting class of ILs where hydrogen bonds (HBs) play an important role: here, "typical" HBs between cations and anions (ca) are competing with "atypical" HBs connecting pairs of cations (cc). We study the equilibrium and kinetics of (cc) and ( c a ) H B s i n 1 -( n -h y d r o x y a l k y l ) -p y r i d i n i u m b i s -(trifluoromethlysulfonyl)imide [HOC n Py][NTf 2 ] ILs by means of molecular dynamics simulations. (cc) HBs are found to be between 0.96 and 3.76 kJ mol −1 stronger than their (ca) counterparts, depending on the alkyl chain length. HB lifetimes and kinetics are analyzed by means of HB population and reactive flux correlation functions. Essentially, four different HB lifetimes have to be considered, spanning about 3 orders of magnitude, each valid in its own right and each associated with different aspects of HB breaking and HB reformation. The long-time limiting behavior of the HB population correlation function is controlled by diffusion of the ions and can be quantitatively described by analytical expressions. The short-time HB behavior is tied to the localized dynamics of the hydroxyl group exploring its local solvation environment. A minimalist kinetic two-domain model is introduced to realistically describe the time evolution of the HB population correlation function for both (ca) and (cc) HBs over 5 orders of magnitude. By employing the reactive flux method, we determine the kinetics of HB breaking, unaffected by diffusion processes. We determine both, the ultrafast upper boundary and the average rate of HB breaking, allowing recrossing-events during the transient relaxation time period. For sufficiently long alkyl chains, all those computed HB lifetimes indicate a higher kinetic stability of (cc) HBs over (ca) HBs; for short chains, it is vice-versa.

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Rotational correlation times, diffusion coefficients and quadrupolar peaks of the protic ionic liquid ethylammonium nitrate by means of 1H fast field cycling NMR relaxometry

Cited by 17 publications

References 91 publications

Coumarin 153 Dynamics in Ethylammonium Nitrate: The Effects of Dilution with Methanol

Coumarin 153 Dynamics in Ethylammonium Nitrate: The Effects of Dilution with Methanol

Molecular Dynamics of Ionic Liquids from Fast-Field Cycling NMR and Molecular Dynamics Simulations

Hydrogen Bonds between Ions of Opposite and Like Charge in Hydroxyl-Functionalized Ionic Liquids: an Exhaustive Examination of the Interplay between Global and Local Motions and Intermolecular Hydrogen Bond Lifetimes and Kinetics

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