Vibrational dynamics of a non-degenerate ultrafast rotor: The (C12,C13)-oxalate ion

Kuroda, Daniel G.; Abdo, Mohannad; Chuntonov, Lev; Smith, Amos B.; Hochstrasser, Robin M.

doi:10.1063/1.4826137

Cited by 15 publications

(17 citation statements)

References 39 publications

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“…For overlapping positive and negative peaks like the bending mode, the loss of correlation is usually observed as the 2D-IR peaks acquiring an upright shape, i.e., more elongated along ω τ . 46-49 Although the time evolution of the H 2 O 2D-IR spectra clearly shows that the positive and negative peaks acquire a vertical elongation within 0.5 ps of waiting time (Figure 2), the tilt of the HDO 2D-IR spectra remains almost unchanged in the same time window.…”

Section: Discussionmentioning

confidence: 96%

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Chuntonov

Kumar

Kuroda

2014

Phys. Chem. Chem. Phys.

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The structure and dynamics of liquid water are further studied by investigating the bend vibrational mode of HDO/D2O and pure H2O via two-dimensional infrared spectroscopy (2D-IR) and linear absorption. The experimental findings and theoretical calculations support a picture in which the HDO bend is localized and the H2O bend is delocalized. The HDO and H2O bends present a loss of the frequency-frequency correlation in subpicosecond time scale. While the loss of correlation for the H2O bend is likely to be associated with the vibrational dynamics of a delocalized transition, the loss of the correlation in the localized HDO bend appears to arise from the fluctuations/rearrangements of the local environment. Interestingly, analysis of the HDO 2D-IR spectra shows the presence of multiple overlapping inhomogeneous distributions of frequencies that interchange in a few picoseconds. Theoretical calculations allow us to propose an atomistic model of the observed vibrational dynamics in which the different in homogeneous distributions and their interchange are assigned to water molecules with different hydrogen-bond states undergoing chemical exchange. The frequency shifts as well as the concentration of the water molecules with single and double hydrogen-bonds as donors derived from the theory are in good agreement with our experimental findings.

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Section: Discussionmentioning

confidence: 96%

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Chuntonov

Kumar

Kuroda

2014

Phys. Chem. Chem. Phys.

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“…The calculation also predicts a ratio of transition dipole moment intensities between the symmetric and asymmetric stretches of 0.06, which is comparable with the 0.04 deduced from the experiments (not shown). Hence, the side band is assigned to the two symmetric CO stretches of W(CO) 6 , which is due to an asymmetry in the solvation shell becoming weakly allowed and having cross peaks with the asymmetric CO stretches of W(CO) 6 via either vibrational energy transfer between symmetric and asymmetric modes − and/or a mechanism involving low-frequency vibrational modes . Interestingly, the symmetric CO stretch (Raman active) was previously reported to be ∼42 cm –1 higher than the asymmetric CO stretch (IR active) .…”

Section: Discussionmentioning

confidence: 91%

Assessing the Location of Ionic and Molecular Solutes in a Molecularly Heterogeneous and Nonionic Deep Eutectic Solvent

et al. 2020

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Deep eutectic solvents (DES) are emerging sustainable designer solvents viewed as greener and better alternatives to ionic liquids. Nonionic DESs possess unique properties such as viscosity and hydrophobicity that make them desirable in microextraction applications such as oil-spill remediation. This work builds upon a nonionic DES, NMA–LA DES, previously designed by our group. The NMA–LA DES presents a rich nanoscopic morphology that could be used to allocate solutes of different polarities. In this work, the possibility of solvating different solutes within the nanoscopically heterogeneous molecular structure of the NMA–LA DES is investigated using ionic and molecular solutes. In particular, the localized vibrational transitions in these solutes are used as reporters of the DES molecular structure via vibrational spectroscopy. The FTIR and 2DIR data suggest that the ionic solute is confined in a polar and continuous domain formed by NMA, clearly sensing the direct effect of the change in NMA concentration. In the case of the molecular nonionic and polar solute, the data indicates that the solute resides in the interface between the polar and nonpolar domains. Finally, the results for the nonpolar and nonionic solute (W(CO)6) are unexpected and less conclusive. Contrary to its polarity, the data suggest that the W(CO)6 resides within the NMA polar domain of the DES, probably by inducing a domain restructuring in the solvent. However, the data are not conclusive enough to discard the possibility that the restructuring comprises not only the polar domain but also the interface. Overall, our results demonstrate that the NMA–LA DES has nanoscopic domains with affinity to particular molecular properties, such as polarity. Thus, the presented results have a direct implication to separation science.

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“…While it is also possible that the cross peak arises from chemical exchange between SSIPs and free TDI and CIPs, the presence of the cross peak at T W = 0 makes the exchange mechanism unlikely since it implies a rate of ion pair formation comparable to the IR excitation pulse duration, i.e., ca. 50–60 fs. ,, Moreover, DFT computations predict a favorable energetics for the ion pair formation on the order of ∼50 kcal/mol (see next section), which is significantly larger than the available thermal energy of system. In addition, the 2D IR spectra for (EMIM)TDI in either DMC or BC at various waiting times (Figure ) display only one set of peaks at 2225 cm –1 , but neither sample presents an obvious cross peak at T W = 0 ps.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, 2D IR spectroscopy also features high-frequency resolution and a second dimension, which provide one not only with the opportunity of resolving peaks not seen in linear spectra , but also with the possibility of determining vibrational coupling among vibrational transitions. ,− This last feature is an essential characteristic for correctly assigning vibrational peaks and their assignment to different species. ,, These two characteristics grant 2D IR spectroscopy with unique insights into the structure and dynamics of systems at a molecular level. Furthermore, 2D IR spectroscopy has been successfully used to study the ion–ion and ion–solvent interactions in a variety of systems. ,− Thus, the use of FTIR and 2D IR allows us to study the structure and dynamics of LiTDI in organic carbonates, as well as to obtain the speciation of the ion. To this end, our study of LiTDI is focused on each pure solvent (DMC and BC) and on their mixtures.…”

Section: Introductionmentioning

confidence: 99%

Effect of Solvation Shell Structure and Composition on Ion Pair Formation: The Case Study of LiTDI in Organic Carbonates

2019

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Organic carbonates are an integral part of commercial lithium-ion batteries due to their desirable properties, such as high dielectric constants. However, the high viscosity of organic carbonates requires the use of mixtures containing a cyclic and a linear carbonate. In binary mixtures, the linear and cyclic organic carbonates compete to solvate the lithium salt. While the preferential solvation has been extensively studied, the effect of the mixed solvation on the ionic speciation of the lithium ion is a topic that has not been studied in detail. In this study, infrared spectroscopies and ab initio chemical computations are utilized to study the change in the solvation structure and dynamics as a function of solvent composition for the model system: lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI). The TDI − nitrile bands are used to probe the changes in the ion speciation as well as in the molecular environment since nitriles are known to be good and sensitive IR spectroscopic reporters of the environment. Our experimental finding shows that the anion forms contact ion pairs, but the amount of contact ion pairs is strongly dependent on the type of carbonate. In particular, TDI − has strong propensity of forming contact ion pairs in linear carbonates, while in cyclic carbonates, it is primarily not directly interacting with Li + . The dynamics of the environment supports our speciation of the anion in both solvents. In addition, the concentration of contact ion pairs shows a monotonic and nonlinear increase with the concentration of linear carbonate in the mixture. Ab initio computations reveal that the nonlinear behavior is related to the energetics of ion pair formation, which appears to be much more favorable when the lithium solvation shell does not contain cyclic carbonates. Overall, our results show that the concentration of linear carbonates in a mixture of organic carbonates directly influences the speciation of the lithium ion.

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Vibrational dynamics of a non-degenerate ultrafast rotor: The (C12,C13)-oxalate ion

Cited by 15 publications

References 39 publications

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Assessing the Location of Ionic and Molecular Solutes in a Molecularly Heterogeneous and Nonionic Deep Eutectic Solvent

Effect of Solvation Shell Structure and Composition on Ion Pair Formation: The Case Study of LiTDI in Organic Carbonates

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