Electrolyte-acetamide molten mixtures

Berchiesi, G.; Angelis, Marco de; Rafaiani, Gianni; Vitali, G.

doi:10.1016/0167-7322(92)80002-y

Cited by 23 publications

(21 citation statements)

References 20 publications

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“…Furthermore, a recent ab initio molecular dynamics simulation study did not find any evidence of charge delocalization in three different choline chloride-based DESs . While many previous experimental studies have centered on the structure and dynamics of components in different acetamide type I DESs, − a few have concentrated on the type III DES, − , which is the motivation of this study. Importantly, the effects of the chemical structure of the hydrogen bond acceptor (HBA) cation on the resulting structure of the DESs remains unexplored.…”

Section: Introductionmentioning

confidence: 84%

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Cui

Kuroda

2018

J. Phys. Chem. A

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The liquid structure of five different amide-based deep eutectic solvents (DESs) as a function of the chemical structure of the hydrogen bond acceptor (HBA) was investigated by linear Fourier transform infrared (FTIR) and two-dimensional infrared (2DIR) spectroscopies. Linear FTIR spectroscopy shows that the amide band of the DESs is not significantly affected by the chemical structure and symmetry of the HBA cation. However, its excitonic nature does not allow us to draw further conclusions. Analysis of the C amide line shapes derived from the 2DIR spectra reveals that the different DESs do not show appreciable differences in the level of disorganization. The vibrational dynamics, derived from the photon echo experiments on theC amide, shows that there is a fast component with a time scale of ∼1 ps irrespective of the HBA. The ultrafast dynamics is assigned to hydrogen bond making and breaking between amides. In addition, a slow dynamical component is observed in the time evolution of the photon echo signal. This contribution appears to be correlated with the asymmetry and polarity of the moieties of the HBA. The overall dynamics is rationalized in terms of a microscopic heterogeneous structure of the DESs, where the heterogeneities create domains that slow the hydrogen bond making and breaking. Molecular dynamics simulations provide additional support for our modeling of the data. In addition, the presence of nanoscopic heterogeneities is consistent with the observation of an endortherm at 23 °C in the differential scanning calorimetry thermogram, which evidenced a phase transition at 23 °C, even though the tested DESs have a melting temperature below -40 °C.

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Section: Introductionmentioning

confidence: 84%

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Cui

Kuroda

2018

J. Phys. Chem. A

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“…19,20 These relatively low frequency measurements have suggested inhomogeneous relaxation kinetics and a colossal static dielectric constant (ε 0 ). Temperature-dependent relaxation times detected in these measurements have been found to spread over half-of-a-second to a couple of nanoseconds, suggesting extremely slow relaxation originating from movements of nanosized domains formed via the interaction between amide molecules and electrolytes.…”

Section: Introductionmentioning

confidence: 98%

Dielectric Relaxations of (Acetamide + Electrolyte) Deep Eutectic Solvents in the Frequency Window, 0.2 ≤ ν/GHz ≤ 50: Anion and Cation Dependence

et al. 2015

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Dielectric relaxation (DR) measurements in the frequency range 0.2 ≤ ν/GHz ≤ 50 have been carried out for neat molten acetamide and six different (acetamide + electrolyte) deep eutectic solvents (DESs) for investigating ion effects on DR dynamics in these ionic DESs. Electrolytes used are lithium salts of bromide (LiBr), nitrate (LiNO3), and perchlorate (LiClO4); sodium salts of perchlorate (NaClO4) and thiocyante (NaSCN); and potassium thiocyanate (KSCN). With these electrolytes acetamide forms DESs approximately at an 80:20 mol ratio. Simultaneous fits to the measured permittivity (ε′) and loss (ε″) spectra of these DESs at ∼293 K require a sum of four Debye (4-D) processes with relaxation times spread over picosecond to nanosecond regime. In contrast, DR spectra for neat molten acetamide (∼354 K) depict 2-D relaxation with time constants ∼50 ps and ∼5 ps. For both the neat and ionic systems, the undetected dispersion, ε∞ – n(D)2, remains to be ∼3–4. Upon comparison, measured DR dynamics reveal pronounced anion and cation effects. Estimated static dielectric constants (ε0) from fits for these DESs cover the range 12 < ε0 < 30 and are remarkably lower than that (ε0 ∼ 64) measured for molten acetamide at ∼354 K. Hydrodynamic effective rotation volumes (Veff) estimated from the slowest DR relaxation time constants vary with ion identity and are much smaller than the molecular volume of acetamide. This decrease of ε0 and Veff is attributed respectively to the pinning of acetamide molecules by ions and orientation jumps and undetected portion to the limited frequency coverage employed in these measurements

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“…13 (b) The melting temperatures (M p ) of acetamide (CH 3 CONH 2 ), propionamide (CH 3 CH 2 CONH 2 ), and butyramide (CH 3 CH 2 CH 2 CONH 2 ) are, respectively, 353 K, 354 K, and 388 K, whereas that of LiClO 4 is 509 K. 22,23 However, mixing of these amides with LiClO 4 at 81:19 mole ratio produces a colourless liquid at a temperature below 298 K. Likewise, LiBr and LiNO 3 are electrolytes with M p > 500 K but upon mixing with acetamide on certain proportions produces colourless liquids near 300 K. Since these mixtures form liquid solutions at temperatures much below the M p of individual components, they are sometime also termed as "supercooled" mixtures. 7,8,[24][25][26] Microheterogeneity in solution structure may also arise in these (alkylamide + electrolyte) DEs as hydrophobic interaction FIG. 1.…”

Section: Introductionmentioning

confidence: 99%

“…52. among alkyl groups and electrostatic interaction between the polar amide group and ions can generate microscopic phase-segregation, leading to formation of microscopic polar and nonpolar domains. [24][25][26] A competition between the lifetime of these domains and the timescale of a reaction occurring in such media then dictates the heterogeneityinduced modulation of a reaction rate. Moreover, different rates of motions of the environmental particles (that is, temporal heterogeneity) [27][28][29][30][31][32] can modify a reaction through dynamic solvent effects.…”

Section: Introductionmentioning

confidence: 99%

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

Guchhait

Das

Daschakraborty

et al. 2014

The Journal of Chemical Physics

167

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Here we investigate the solute-medium interaction and solute-centered dynamics in (RCONH2 + LiX) deep eutectics (DEs) via carrying out time-resolved fluorescence measurements and all-atom molecular dynamics simulations at various temperatures. Alkylamides (RCONH2) considered are acetamide (CH3CONH2), propionamide (CH3CH2CONH2), and butyramide (CH3CH2CH2CONH2); the electrolytes (LiX) are lithium perchlorate (LiClO4), lithium bromide (LiBr), and lithium nitrate (LiNO3). Differential scanning calorimetric measurements reveal glass transition temperatures (T(g)) of these DEs are ~195 K and show a very weak dependence on alkyl chain-length and electrolyte identity. Time-resolved and steady state fluorescence measurements with these DEs have been carried out at six-to-nine different temperatures that are ~100-150 K above their individual T(g)s. Four different solute probes providing a good spread of fluorescence lifetimes have been employed in steady state measurements, revealing strong excitation wavelength dependence of probe fluorescence emission peak frequencies. Extent of this dependence, which shows sensitivity to anion identity, has been found to increase with increase of amide chain-length and decrease of probe lifetime. Time-resolved measurements reveal strong fractional power dependence of average rates for solute solvation and rotation with fraction power being relatively smaller (stronger viscosity decoupling) for DEs containing longer amide and larger (weaker decoupling) for DEs containing perchlorate anion. Representative all-atom molecular dynamics simulations of (CH3CONH2 + LiX) DEs at different temperatures reveal strongly stretched exponential relaxation of wavevector dependent acetamide self dynamic structure factor with time constants dependent both on ion identity and temperature, providing justification for explaining the fluorescence results in terms of temporal heterogeneity and amide clustering in these multi-component melts.

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Electrolyte-acetamide molten mixtures

Cited by 23 publications

References 20 publications

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Dielectric Relaxations of (Acetamide + Electrolyte) Deep Eutectic Solvents in the Frequency Window, 0.2 ≤ ν/GHz ≤ 50: Anion and Cation Dependence

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

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