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Deshmukh SH, Nachaki EO, Kuroda DG. Uncovering the binding nature of thiocyanate in contact ion pairs with lithium ions. J Chem Phys 2024; 161:034507. [PMID: 39017430 DOI: 10.1063/5.0216491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Accepted: 06/28/2024] [Indexed: 07/18/2024] Open
Abstract
Ion pair formation is a fundamental molecular process that occurs in a wide variety of systems, including electrolytes, biological systems, and materials. In solution, the thiocyanate (SCN-) anion interacts with cations to form contact ion pairs (CIPs). Due to its ambidentate nature, thiocyanate can bind through either its sulfur or nitrogen atoms, depending on the solvent. This study focuses on the binding nature of thiocyanate with lithium ions as a function of the solvents using FTIR, 2D infrared spectroscopy (2DIR) spectroscopies, and theoretical calculations. The study reveals that the SCN- binding mode (S or N end) in CIPs can be identified through 2DIR spectroscopy but not by linear IR spectroscopy. Linear IR spectroscopy shows that the CN stretch frequencies are too close to one another to separate N- and S-bound CIPs. Moreover, the IR spectrum shows that the S-C stretch presents different frequencies for the salt in different solvents, but it is related to the anion speciation rather than to its binding mode. A similar trend is observed for the anion bend. 2DIR spectra show different dynamics for N-bound and S-bound thiocyanate. In particular, the frequency-frequency correlation function (FFCF) dynamics extracted from the 2DIR spectra have a single picosecond exponential decay for N-bound thiocyanate and a biexponential decay for S-bound thiocyanate, consistent with the binding mode of the anion. Finally, it is also observed that the binding mode also affects the line shape parameters, probably due to the different molecular mechanisms of the FFCF for N- and S-bound CIPs.
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Affiliation(s)
- Samadhan H Deshmukh
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Ernest O Nachaki
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Daniel G Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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2
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Nachaki E, Kuroda DG. Transitioning from Regular Electrolytes to Solvate Ionic Liquids to High-Concentration Electrolytes: Changes in Transport Properties and Ionic Speciation. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:11522-11533. [PMID: 39050925 PMCID: PMC11264273 DOI: 10.1021/acs.jpcc.4c02248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 06/18/2024] [Accepted: 07/03/2024] [Indexed: 07/27/2024]
Abstract
Glyme-based lithium-ion electrolytes have received considerable attention from the scientific community due to their improved safety, as well as electrochemical and thermal stability over carbonate-based electrolytes. However, these electrolytes suffer from major drawbacks such as high viscosities. To overcome the challenges that hinder their full potential, the molecular description of glyme-based lithium electrolytes in the high-concentration regime, particularly in the solvate ionic liquid (SIL) and high-concentration electrolyte (HCE) regimes, is needed. In this study, model glyme-based electrolytes based on a lithium thiocyanate and either tetraglyme (G4) or a mixture of monoglyme (G1) and diglyme (G2) were investigated as a function of the solvent-to-lithium ratio using linear and nonlinear IR spectroscopies, in combination with ab initio computations as well as electrochemical methods . The transport properties reveal enhanced ionicities in the HCE and SIL regimes ([O]/[Li] ≤ 5) compared to the regular electrolytes (REs, with [O]/[Li] > 5) in both pure (G4) and mixed (G1:G2) glymes. IR and ab initio computations relate these larger ionicities to the higher concentration of charged aggregates in the HCE and SIL electrolytes ([O]/[Li] ≤ 5). Moreover, it was observed that the use of mixed glymes appears to have a minimal effect on the transport properties of REs but exhibits deleterious effects on SILs. Overall, the results provide a molecular framework for describing the local structure of lithium glyme-based electrolytes and demonstrate the key role that the nature of glyme solvation plays in the molecular structure and consequently the macroscopic properties of the Li-glyme SILs, HCEs, and REs.
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Affiliation(s)
- Ernest
O. Nachaki
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Daniel G. Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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3
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Zhang M, Gao Y, Fu L, Bai Y, Mukherjee S, Chen CL, Liu J, Bian H, Fang Y. Chain-like Structures Facilitate Li + Transport in Concentrated Aqueous Electrolytes: Insights from Ultrafast Infrared Spectroscopy and Molecular Dynamics Simulations. J Phys Chem Lett 2023; 14:6968-6976. [PMID: 37506173 DOI: 10.1021/acs.jpclett.3c01494] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/30/2023]
Abstract
Highly concentrated aqueous electrolytes have attracted attention due to their unique applications in lithium ion batteries (LIBs). However, the solvation structure and transport mechanism of Li+ cations at concentrated concentrations remain largely unexplored. To address this gap in knowledge, we employ ultrafast infrared spectroscopy and molecular dynamics (MD) simulations to reveal the dynamic and spatial structural heterogeneity in aqueous lithium chloride (LiCl) solutions. The coupling between the reorientation dynamics of the extrinsic probe and the macroscopic viscosity in aqueous LiCl solutions was analyzed using the Stokes-Einstein-Debye (SED) equations. MD simulations reveal that the Cl- and Li+ form chain-like structures through electrostatic interactions, supporting the vehicular migration of Li+ through the chain-like structure. The concentration dependent conductivity of the LiCl solution is well reproduced, where Li(H2O)2+ and Li(H2O)3+ are the dominant species that contribute to the conduction of Li+. This study is expected to establish correlations between ion pair structures and macroscopic properties.
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Affiliation(s)
- Miaomiao Zhang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Yuting Gao
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Lanya Fu
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Yimin Bai
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Somnath Mukherjee
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Cheng-Lung Chen
- Department of Chemistry, National Sunyat-sen University, Kaohsiung, 80424, China
| | - Jing Liu
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Hongtao Bian
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Yu Fang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China
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4
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Tibbetts CA, Wyatt AB, Luther BM, Rappé AK, Krummel AT. Dicyanamide Anion Reports on Water Induced Local Structural and Dynamic Heterogeneity in Ionic Liquid Mixtures. J Phys Chem B 2023; 127:932-943. [PMID: 36655844 DOI: 10.1021/acs.jpcb.2c07060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The effects of limited amounts (under 21.6% χWater) of water on 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) and 1-butyl-3-methylimidazolium dicyanamide (BmimDCA) room-temperature ionic liquid (RTIL) mixtures were characterized by tracking changes in the linear and two-dimensional infrared (2D IR) vibrational features of the dicyanamide anion (DCA). Peak shifts with increasing water suggest the formation of water-associated and nonwater-associated DCA populations. Further results showed clear differences in the dynamic behavior of these different populations of DCA at low (defined here as below 2.5% χWater), mid (defined here as between 2.5% χWater and 9.6% χWater), and high (defined here as between 11.6% χWater and 21.6% χWater) range water concentrations. Vibrational relaxation is accelerated with increasing water content for water-associated populations of DCA, indicating water facilitates population relaxation, possibly through the provision of additional bath modes. Conversely, spectral diffusion of water-associated populations slowed dramatically with increasing water, suggesting that water drives the formation of distinct and noninterchangeable or very slowly interchangeable local solvent environments.
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Affiliation(s)
- Clara A Tibbetts
- Department of Chemistry, Colorado State University, Fort Collins, Colorado80523-1972, United States
| | - Autumn B Wyatt
- Department of Chemistry, Colorado State University, Fort Collins, Colorado80523-1972, United States
| | - Bradley M Luther
- Department of Chemistry, Colorado State University, Fort Collins, Colorado80523-1972, United States
| | - Anthony K Rappé
- Department of Chemistry, Colorado State University, Fort Collins, Colorado80523-1972, United States
| | - Amber T Krummel
- Department of Chemistry, Colorado State University, Fort Collins, Colorado80523-1972, United States
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5
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Zhu F, Ge J, Gao Y, Li S, Chen Y, Tu J, Wang M, Jiao S. Molten salt electro-preparation of graphitic carbons. EXPLORATION (BEIJING, CHINA) 2023; 3:20210186. [PMID: 37323618 PMCID: PMC10191008 DOI: 10.1002/exp.20210186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 04/15/2022] [Indexed: 06/17/2023]
Abstract
Graphite has been used in a wide range of applications since the discovery due to its great chemical stability, excellent electrical conductivity, availability, and ease of processing. However, the synthesis of graphite materials still remains energy-intensive as they are usually produced through a high-temperature treatment (>3000°C). Herein, we introduce a molten salt electrochemical approach utilizing carbon dioxide (CO2) or amorphous carbons as raw precursors for graphite synthesis. With the assistance of molten salts, the processes can be conducted at moderate temperatures (700-850°C). The mechanisms of the electrochemical conversion of CO2 and amorphous carbons into graphitic materials are presented. Furthermore, the factors that affect the graphitization degree of the prepared graphitic products, such as molten salt composition, working temperature, cell voltage, additives, and electrodes, are discussed. The energy storage applications of these graphitic carbons in batteries and supercapacitors are also summarized. Moreover, the energy consumption and cost estimation of the processes are reviewed, which provides perspectives on the large-scale synthesis of graphitic carbons using this molten salt electrochemical strategy.
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Affiliation(s)
- Fei Zhu
- State Key Laboratory of Advanced MetallurgyUniversity of Science and Technology BeijingBeijingChina
- Beijing Key Laboratory of Green Recycling and Extraction of MetalsUniversity of Science and Technology BeijingBeijingChina
| | - Jianbang Ge
- School of Metallurgical and Ecological EngineeringUniversity of Science and Technology BeijingBeijingChina
| | - Yang Gao
- School of Metallurgical and Ecological EngineeringUniversity of Science and Technology BeijingBeijingChina
| | - Shijie Li
- Institute of Advanced Structure TechnologyBeijing Institute of TechnologyBeijingChina
| | - Yunfei Chen
- State Key Laboratory of Advanced MetallurgyUniversity of Science and Technology BeijingBeijingChina
- Beijing Key Laboratory of Green Recycling and Extraction of MetalsUniversity of Science and Technology BeijingBeijingChina
| | - Jiguo Tu
- State Key Laboratory of Advanced MetallurgyUniversity of Science and Technology BeijingBeijingChina
- Beijing Key Laboratory of Green Recycling and Extraction of MetalsUniversity of Science and Technology BeijingBeijingChina
| | - Mingyong Wang
- State Key Laboratory of Advanced MetallurgyUniversity of Science and Technology BeijingBeijingChina
- Beijing Key Laboratory of Green Recycling and Extraction of MetalsUniversity of Science and Technology BeijingBeijingChina
| | - Shuqiang Jiao
- School of Metallurgical and Ecological EngineeringUniversity of Science and Technology BeijingBeijingChina
- State Key Laboratory of Advanced MetallurgyUniversity of Science and Technology BeijingBeijingChina
- Beijing Key Laboratory of Green Recycling and Extraction of MetalsUniversity of Science and Technology BeijingBeijingChina
- Institute of Advanced Structure TechnologyBeijing Institute of TechnologyBeijingChina
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6
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Biswas A, Mallik BS. Direct Correlation between Short-Range Vibrational Spectral Diffusion and Localized Ion-Cage Dynamics of Water-in-Salt Electrolytes. J Phys Chem B 2023; 127:236-248. [PMID: 36575973 DOI: 10.1021/acs.jpcb.2c04391] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The molecular dynamics simulations of a "water-in-salt" electrolyte, lithium bis(trifluoromethyl sulfonyl) imide (LiNTf2), with a varying concentration range of 3 to 20 m were performed to establish a direct connection between a dynamic property like the ion-cage lifetime with the short-range vibrational stretching frequency shift of the used probe, HOD. The properties reported here are compared to that obtained from experiments performed at the same concentrations. The time-series wavelet transform was adopted as a preferable mathematical tool for calculating the instantaneous fluctuating frequencies of the probe O-D stretch mode and the concentration-dependent vibrational stretch spectral signature based on the variable functions associated with a particular chemical bond derived from classical molecular dynamics trajectories. The decay time constants of frequency fluctuations and the lifetime of the ion cage (τIC) were estimated as a function of salt concentration. Herein, we emphasize the correlation between the slowest time constant (τ3) of the decay of O-D stretch frequency fluctuations and the timescales associated with the lifetime of ion cages (τIC). The results exhibit that the existing relationships were also concentration-dependent. Therefore, this study highlights the connection between the ionic motions that regulate the overall system dynamics with the short-range vibrational frequency shift of the used probe, which was used similar to experiments. It also provides an understanding of the interionic interactions and the dynamical and spectral properties of the electrolytic mixtures. We establish a direct correlation between short-range frequency profile and localized ion-cage lifetime, which can fill the gap of understanding between viscosity, vibrational frequency, and ion-cage dynamics of electrolytes.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
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7
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Biswas A, Mallik BS. Molecular Simulation-Guided Spectroscopy of Imidazolium-Based Ionic Liquids and Effects of Methylation on Ion-Cage and -Pair Dynamics. J Phys Chem B 2022; 126:8838-8850. [PMID: 36264223 DOI: 10.1021/acs.jpcb.2c04901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Classical molecular dynamics simulations were performed to assess an atomistic interpretation of the ion-probe structural interactions in two typical ionic liquids (ILs), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIm][NTf2] and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [BDimIm][NTf2] through computational ultrafast spectroscopy. The nitrile stretching vibrations of the thiocyanate anion, [SCN]-, serve as the local mode of the ultrafast system dynamics within the imidazolium-based ionic liquid environment. The wavelet transform of classical trajectories determines the time-varying fluctuating frequencies and the stretch spectral signatures of SCN- in the normalized distribution. However, computational modeling of the two-dimensional (2D) spectra from the wavelet-derived vibrational frequencies yields time evolution of the local molecular structure along with the varied time-dependent dynamics of the spectral diffusion process. We calculated the frequency-frequency correlation functions (FFCFs), time correlations associated with the ion-pair and -cage dynamics, and mean square displacements as a function of time, depicting diffusive dynamics. The calculated results based on the pair correlation functions and the distribution of atomic density suggest that the hydrogen and methylated carbon at the two-position of the imidazolium ring of [BMIm] and [BDimIm] cations, respectively, strongly interact with the probe through the N of the thiocyanate anion rather than the S atom. The center-of-mass center-of-mass (COM-COM) cation-probe radial distribution functions (RDFs) in conjunction with the site-specific structural analysis further reveal well-structured interactions of the thiocyanate ion and [BMIm]+ cation rather than the [BDimIm] cation. In contrast, the anion-probe COM-COM RDFs depict weak interactive associations within the vibrational probe [SCN]- and [NTf2]- ions. Methylation at the two-position of the imidazolium ring predicts slower structural reorganization and breaking and reformation dynamics of the ion pairs and cages within the ionic liquid framework.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
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8
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Dynamics in tris(pentafluoroethyl)trifluorophosphate (FAP) anion based ionic liquids: A 2D-IR study with tungsten hexacarbonyl. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Ghosh D, Sakpal SS, Chatterjee S, Deshmukh SH, Kwon H, Kim YS, Bagchi S. Association-Dissociation Dynamics of Ionic Electrolytes in Low Dielectric Medium. J Phys Chem B 2021; 126:239-248. [PMID: 34961310 DOI: 10.1021/acs.jpcb.1c08613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ionic electrolytes are known to form various complexes which exist in dynamic equilibrium in a low dielectric medium. However, structural characterization of these complexes has always posed a great challenge to the scientific community. An additional challenge is the estimation of the dynamic association-dissociation time scales (lifetime of the complexes), which are key to the fundamental understanding of ion transport. In this work, we have used a combination of infrared absorption spectroscopy, two-dimensional infrared spectroscopy, molecular dynamics simulations, and density functional theory calculations to characterize the various ion complexes formed by the thiocyanate-based ionic electrolytes as a function of different cations in a low dielectric medium. Our results demonstrate that thiocyanate is an excellent vibrational reporter of the heterogeneous ion complexes undergoing association-dissociation dynamics. We find that the ionic electrolytes exist as contact ion pairs, dimers, and clusters in a low dielectric medium. The relative ratios of the various ion complexes are sensitive to the cations. In addition to the interactions between the thiocyanate anion and the countercation, the solute-solvent interactions drive the dynamic equilibrium. We have estimated the association-dissociation dynamics time scales from two-dimensional infrared spectroscopy. The exchange time scale involving the cluster is faster than that between a dimer and an ion pair. Moreover, we find that the dynamic equilibrium between the cluster and another ion complex is correlated to the solvent fluctuations.
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Affiliation(s)
- Deborin Ghosh
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
| | - Sushil S Sakpal
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Srijan Chatterjee
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Samadhan H Deshmukh
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Hyejin Kwon
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 44919, Korea
| | - Yung Sam Kim
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 44919, Korea
| | - Sayan Bagchi
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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10
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Robben KC, Cheatum CM. Least-Squares Fitting of Multidimensional Spectra to Kubo Line-Shape Models. J Phys Chem B 2021; 125:12876-12891. [PMID: 34783568 PMCID: PMC8630800 DOI: 10.1021/acs.jpcb.1c08764] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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We report a comprehensive
study of the efficacy of least-squares
fitting of multidimensional spectra to generalized Kubo line-shape
models and introduce a novel least-squares fitting metric, termed
the scale invariant gradient norm (SIGN), that enables a highly reliable
and versatile algorithm. The precision of dephasing parameters is
between 8× and 50× better for nonlinear model fitting compared
to that for the centerline-slope (CLS) method, which effectively increases
data acquisition efficiency by 1–2 orders of magnitude. Whereas
the CLS method requires sequential fitting of both the nonlinear and
linear spectra, our model fitting algorithm only requires nonlinear
spectra but accurately predicts the linear spectrum. We show an experimental
example in which the CLS time constants differ by 60% for independent
measurements of the same system, while the Kubo time constants differ
by only 10% for model fitting. This suggests that model fitting is
a far more robust method of measuring spectral diffusion than the
CLS method, which is more susceptible to structured residual signals
that are not removable by pure solvent subtraction. Statistical analysis
of the CLS method reveals a fundamental oversight in accounting for
the propagation of uncertainty by Kubo time constants in the process
of fitting to the linear absorption spectrum. A standalone desktop
app and source code for the least-squares fitting algorithm are freely
available, with example line-shape models and data. We have written
the MATLAB source code in a generic framework where users may supply
custom line-shape models. Using this application, a standard desktop
fits a 12-parameter generalized Kubo model to a 106 data-point
spectrum in a few minutes.
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Affiliation(s)
- Kevin C Robben
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
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11
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Cui Y, Rushing JC, Seifert S, Bedford NM, Kuroda DG. Structural and dynamical changes observed when transitioning from an ionic liquid to a deep eutectic solvent. J Chem Phys 2021; 155:054507. [PMID: 34364351 DOI: 10.1063/5.0053448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The microscopic molecular structure and dynamics of a new deep eutectic solvent (DES) composed of an ionic liquid (1-hexyl-3-methylimidazolium chloride) and an amide (trifluoroacetamide) at various molar ratios were investigated using linear and non-linear infrared spectroscopy with a vibrational probe. The use of the ionic liquid allows us to investigate the changes that the system undergoes with the addition of the amide or, equivalently, the changes from an ionic liquid to a DES. Our studies revealed that the vibrational probe in the DES senses a very similar local environment irrespective of the cation chemical structure. In addition, the amide also appears to perceive the same molecular environment. The concentration dependence studies also showed that the amide changes from being isolated from other amides in the ionic liquid environment to an environment where the amide-amide interactions are favored. In the case of the vibrational probe, the addition of the amide produced significant changes in the slow dynamics associated with the making and breaking of the ionic cages but did not affect the rattling-in-cage motions perceived by it. Furthermore, the concentration dependence of slow dynamics showed two regimes which are linked to the changes in the overall structure of the solution. These observations are interpreted in the context of a nanoscopic heterogeneous environment in the DES which, according to the observed dynamical regimes, appears at very large concentrations of the amide (molar ratio of greater than 1:1) since for lower amide molar ratios, the amide appears to be not segregated from the ionic liquid. This proposed molecular picture is supported by small angle x-ray scattering experiments.
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Affiliation(s)
- Yaowen Cui
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Jeramie C Rushing
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Soenke Seifert
- X-Ray Sciences Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Nicholas M Bedford
- School of Chemical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Daniel G Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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12
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Biswas A, Mallik BS. Dynamics of Ionic Liquid through Intrinsic Vibrational Probes Using the Dispersion-Corrected DFT Functionals. J Phys Chem B 2021; 125:6994-7008. [PMID: 34142827 DOI: 10.1021/acs.jpcb.1c04960] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
First principles molecular dynamics simulations have been utilized to study the spectral properties of the protic ionic liquid, methylammonium formate (MAF). All simulations were performed using density functional theory (DFT) and various van der Waals-corrected exchange-correlation functionals. We calculated the vibrational stretch frequency distributions, determined the time-frequency correlations of the intrinsic vibrational probes, the N-H and C-O modes in MAF, and the frequency-structure correlations. We also estimated the average hydrogen-bond lifetimes and orientation dynamics to capture the ultrafast spectral response. The spectroscopic signature of the N-H stretching vibrations using the Becke-Lee-Yang-Parr (BLYP) and Perdew-Burke-Ernzerhof (PBE) functionals displays a spectral shift in the lower frequency side, suggesting stronger hydrogen-bonding interactions represented by the gradient approximation functionals than the van der Waals (vdW)-corrected simulations. The carboxylate frequency profiles with the dispersion-corrected representations are almost similar without a significant difference in the normalized distributions. Besides, the COO stretching frequencies at the peak maxima positions of the PBE functionals exhibit a lesser deviation from the experimental data. Spectral diffusion dynamics of the intrinsic vibrational probes on the cationic and anionic sites of the ionic liquid proceed through a short time relaxation of the intact hydrogen bonds followed by an intermediate time constant and a longer time decay indicating the switchover of hydrogen bonds. Dispersion-corrected atom-centered one-electron potential (DCACP) correction added to the BLYP system slows down the picosecond time scales of frequency correlation and the time constants of rotational motion, lengthening the overall system dynamics. The observed trends in the time-dependent decays of frequency fluctuations and the orientation autocorrelation functions correlate with the structural interactions in liquid MAF and hydrogen-bond dynamics. In this study, we examine the predictions made by different density functional treatments comparing the results of the uncorrected BLYP and PBE representations with the semiempirical vdW methods of Grimme and matching our calculated data with the experimental observations.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
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13
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Johnson CA, Parker AW, Donaldson PM, Garrett-Roe S. An ultrafast vibrational study of dynamical heterogeneity in the protic ionic liquid ethyl-ammonium nitrate. I. Room temperature dynamics. J Chem Phys 2021; 154:134502. [PMID: 33832238 DOI: 10.1063/5.0044822] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using ultrafast two-dimensional infrared spectroscopy (2D-IR), a vibrational probe (thiocyanate, SCN-) was used to investigate the hydrogen bonding network of the protic ionic liquid ethyl-ammonium nitrate (EAN) in comparison to H2O. The 2D-IR experiments were performed in both parallel (⟨ZZZZ⟩) and perpendicular (⟨ZZXX⟩) polarizations at room temperature. In EAN, the non-Gaussian lineshape in the FTIR spectrum of SCN- suggests two sub-ensembles. Vibrational relaxation rates extracted from the 2D-IR spectra provide evidence of the dynamical differences between the two sub-ensembles. We support the interpretation of two sub-ensembles with response function simulations of two overlapping bands with different vibrational relaxation rates and, otherwise, similar dynamics. The measured rates for spectral diffusion depend on polarization, indicating reorientation-induced spectral diffusion (RISD). A model of restricted molecular rotation (wobbling in a cone) fully describes the observed spectral diffusion in EAN. In H2O, both RISD and structural spectral diffusion contribute with similar timescales. This complete characterization of the dynamics at room temperature provides the basis for the temperature-dependent measurements in Paper II of this series.
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Affiliation(s)
- Clinton A Johnson
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, USA
| | - Anthony W Parker
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Harwell Campus, Didcot, United Kingdom
| | - Paul M Donaldson
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Harwell Campus, Didcot, United Kingdom
| | - Sean Garrett-Roe
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, USA
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14
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Sha M, Yamada SA, Fayer MD. Orientational Pair Correlations and Local Structure of Benzonitrile from Molecular Dynamics Simulations with Comparisons to Experiments. J Phys Chem B 2021; 125:3163-3177. [PMID: 33730488 DOI: 10.1021/acs.jpcb.0c11148] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present an experimentally parametrized molecular dynamics study of single-molecule and collective orientational relaxation in neat benzonitrile through the analysis of the reorientational anisotropy and polarizability anisotropy time correlation function (PA-TCF). The simulations show that the PA-TCF is dominated by collective reorientation after 20 ps. Collective reorientation is found to be slower than single-molecule reorientation by a factor of 1.67, consistent with recent experiments. The simulations provide direct evidence of local antiparallel benzonitrile configurations. These structures, which have been the center of some debate, are responsible for the slower rate of collective versus single-molecule reorientation in the liquid. Further structural analysis indicates that significant Coulombic interactions between the nitrile group and hydrogen atoms on adjacent molecules play a role in the formation of the antiparallel structures. The single-molecule dynamics reflected in the anisotropy are complex and consist of a ballistic regime, restricted angular diffusion, and spatially anisotropic free diffusion. The principal components of the rotational diffusion tensor are independently obtained and shown to reproduce the free diffusion regime of the anisotropy for each principal axis according to the predictions of a previous theory.
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Affiliation(s)
- Maolin Sha
- Department of Physics and Materials Engineering, Hefei Normal University, Hefei 230061, China
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Steven A Yamada
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael D Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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15
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Biswas A, Mallik BS. Ultrafast Aqueous Dynamics in Concentrated Electrolytic Solutions of Lithium Salt and Ionic Liquid. J Phys Chem B 2020; 124:9898-9912. [DOI: 10.1021/acs.jpcb.0c06221] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Bhabani S. Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
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16
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Zhou D, Hao H, Ma Y, Zhong H, Dai Y, Cai K, Mukherjee S, Liu J, Bian H. Specific Host-Guest Interactions in the Crown Ether Complexes with K + and NH 4+ Revealed from the Vibrational Relaxation Dynamics of the Counteranion. J Phys Chem B 2020; 124:9154-9162. [PMID: 32965118 DOI: 10.1021/acs.jpcb.0c07032] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The specific host-guest interactions in the corresponding complexes of K+ and NH4+ with typical crown ethers were investigated by using FTIR and ultrafast IR spectroscopies. The counteranions, i.e., SCN-, were employed as a local vibrational probe to report the structural dynamics of the complexation. It was found that the vibrational relaxation dynamics of the SCN- was strongly affected by the cations confined in the cavities of the crown ethers. The time constant of the vibrational population decay of SCN- in the complex of NH4+ with the 18-crown-6 was determined to be 6 ± 2 ps, which is ∼30 times faster than that in the complex of K+ with the crown ethers. Control experiments showed that the vibrational population decay of SCN- depended on the size of the cavities of the crown ethers. A theoretical calculation further indicated that the nitrogen atom of SCN- showed preferential coordination to the K+ ions hosted by the crown ethers, while the NH4+ can form hydrogen bonds with the oxygen atoms in the studied crown ethers. The geometric constraints formed in the complex of crown ethers can cause a specific interaction between the NH4+ and SCN-, which can facilitate the intermolecular vibrational energy redistribution of the SCN-.
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Affiliation(s)
- Dexia Zhou
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Hongxing Hao
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Yinhua Ma
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Hongmei Zhong
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou, Fujian 350007, China
| | - Ya'nan Dai
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou, Fujian 350007, China
| | - Kaicong Cai
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou, Fujian 350007, China
| | - Somnath Mukherjee
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Jing Liu
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Hongtao Bian
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
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17
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Hong J, Zhou DX, Hao HX, Zhao M, Bian HT. Ultrafast infrared spectroscopic study of microscopic structural dynamics in pH stimulus-responsive hydrogels. CHINESE J CHEM PHYS 2020. [DOI: 10.1063/1674-0068/cjcp2006096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Jian Hong
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - De-xia Zhou
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - Hong-xing Hao
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - Min Zhao
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - Hong-tao Bian
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
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18
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Pennathur AK, Voegtle MJ, Menachekanian S, Dawlaty JM. Strong Propensity of Ionic Liquids in Their Aqueous Solutions for an Organic-Modified Metal Surface. J Phys Chem B 2020; 124:7500-7507. [PMID: 32786711 DOI: 10.1021/acs.jpcb.0c04665] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Understanding ionic structure and electrostatic environments near a surface has both fundamental and practical value. In electrochemistry, especially when room temperature ionic liquids (ILs) are involved, the complex ionic structure near the interface is expected to crucially influence reactions. Here we report evidence that even in dilute aqueous solutions of several ILs, the ions aggregate near the surface in ways that are qualitatively different from simple electrolytes. We have used a vibrational probe molecule, 4-mercaptobenzonitrile (MBN), tethered to a metal surface to monitor the behavior of the ionic layers. The characteristic nitrile vibrational frequency of this molecule has distinct values in the presence of pure water (∼2232 cm-1) and pure IL (for example, ∼2226 cm-1 for ethylmethylimidazolium tetrafluoroborate, [EMIM][BF4]). This difference reflects the local electrostatic field and the hydrogen-bonding variations between these two limiting cases. We tracked this frequency shift as a function of IL concentration in water all the way from pure water to pure IL. We report two important findings. First, only one nitrile peak is observed for the entire concentration range, indicating that at least on the length scale of the probe molecule water and ILs do not phase separate within the interface, and no heterogeneously distinct electrostatic environments are formed. Second, and more importantly, we find that even up to a significant mole fraction of bulk water (x ∼ 0.95), the nitrile frequency does not change from that indicative of a pure IL for [EMIM][BF4], indicating preferential aggregation of the ions near the surface. Because this behavior is very similar to surfactants, we chose an imidazolium cation with a longer side chain which resulted in behavior expected from a surfactant, with a preferential layer of the ions on the surface even in dilute water solutions (x ∼ 0.995). This observation indicates that even those ILs that are not nominally categorized as surfactants have a strong tendency to aggregate at the surface. Because ILs serve as electrolytes in a range of electrochemical reactions, including those requiring water, our results are likely useful for mechanistic understanding and tuning of such reactions.
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Affiliation(s)
- Anuj K Pennathur
- Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States
| | - Matthew J Voegtle
- Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States
| | - Sevan Menachekanian
- Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States
| | - Jahan M Dawlaty
- Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States
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19
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Wang YL, Li B, Sarman S, Mocci F, Lu ZY, Yuan J, Laaksonen A, Fayer MD. Microstructural and Dynamical Heterogeneities in Ionic Liquids. Chem Rev 2020; 120:5798-5877. [PMID: 32292036 PMCID: PMC7349628 DOI: 10.1021/acs.chemrev.9b00693] [Citation(s) in RCA: 197] [Impact Index Per Article: 49.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 12/11/2022]
Abstract
Ionic liquids (ILs) are a special category of molten salts solely composed of ions with varied molecular symmetry and charge delocalization. The versatility in combining varied cation-anion moieties and in functionalizing ions with different atoms and molecular groups contributes to their peculiar interactions ranging from weak isotropic associations to strong, specific, and anisotropic forces. A delicate interplay among intra- and intermolecular interactions facilitates the formation of heterogeneous microstructures and liquid morphologies, which further contributes to their striking dynamical properties. Microstructural and dynamical heterogeneities of ILs lead to their multifaceted properties described by an inherent designer feature, which makes ILs important candidates for novel solvents, electrolytes, and functional materials in academia and industrial applications. Due to a massive number of combinations of ion pairs with ion species having distinct molecular structures and IL mixtures containing varied molecular solvents, a comprehensive understanding of their hierarchical structural and dynamical quantities is of great significance for a rational selection of ILs with appropriate properties and thereafter advancing their macroscopic functionalities in applications. In this review, we comprehensively trace recent advances in understanding delicate interplay of strong and weak interactions that underpin their complex phase behaviors with a particular emphasis on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions.
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Affiliation(s)
- Yong-Lei Wang
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Bin Li
- School
of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, P. R. China
| | - Sten Sarman
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Francesca Mocci
- Department
of Chemical and Geological Sciences, University
of Cagliari, I-09042 Monserrato, Italy
| | - Zhong-Yuan Lu
- State
Key Laboratory of Supramolecular Structure and Materials, Institute
of Theoretical Chemistry, Jilin University, Changchun 130021, P. R. China
| | - Jiayin Yuan
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Aatto Laaksonen
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
- State
Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
- Centre of
Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, 41A, 700487 Iasi, Romania
- Department
of Engineering Sciences and Mathematics, Division of Energy Science, Luleå University of Technology, SE-97187 Luleå, Sweden
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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20
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Chen X, Cui Y, Gobeze HB, Kuroda DG. Assessing the Location of Ionic and Molecular Solutes in a Molecularly Heterogeneous and Nonionic Deep Eutectic Solvent. J Phys Chem B 2020; 124:4762-4773. [PMID: 32421342 PMCID: PMC7304071 DOI: 10.1021/acs.jpcb.0c02482] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
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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Affiliation(s)
- Xiaobing Chen
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Yaowen Cui
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Habtom B Gobeze
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Daniel G Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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21
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Lane PD, Reichenbach J, Farrell AJ, Ramakers LAI, Adamczyk K, Hunt NT, Wynne K. Experimental observation of nanophase segregation in aqueous salt solutions around the predicted liquid-liquid transition in water. Phys Chem Chem Phys 2020; 22:9438-9447. [PMID: 32314750 DOI: 10.1039/c9cp06082k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The liquid-liquid transition in supercooled liquid water, predicted to occur around 220 K, is controversial due to the difficulty of studying it caused by competition from ice crystallization (the so-called "no man's land"). In aqueous solutions, it has been predicted to give rise to phase separation on a nanometer scale between a solute-rich high-density phase and a water-rich low-density phase. Here we report direct experimental evidence for the formation of a nanosegregated phase in eutectic aqueous solutions of LiCl and LiSCN where the presence of crystalline water can be experimentally excluded. Femtosecond infrared and Raman spectroscopies are used to determine the temperature-dependent structuring of water, the solvation of the SCN- anion, and the size of the phase segregated domains.
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Affiliation(s)
- Paul D Lane
- Department of Physics, SUPA, University of Strathclyde, Glasgow, UK.
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22
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Guchhait B, Tibbetts CA, Tracy KM, Luther BM, Krummel AT. Ultrafast vibrational dynamics of a trigonal planar anionic probe in ionic liquids (ILs): A two-dimensional infrared (2DIR) spectroscopic investigation. J Chem Phys 2020; 152:164501. [PMID: 32357764 DOI: 10.1063/1.5141751] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A major impediment limiting the widespread application of ionic liquids (ILs) is their high shear viscosity. Incorporation of a tricyanomethanide (TCM-) anion in ILs leads to low shear viscosity and improvement of several characteristics suitable for large scale applications. However, properties including interactions of TCM- with the local environment and dynamics of TCM- have not been thoroughly investigated. Herein, we have studied the ultrafast dynamics of TCM- in several imidazolium ILs using linear IR and two-dimensional infrared spectroscopy techniques. The spectral diffusion dynamics of the CN stretching modes of TCM- in all ILs exhibit a nonexponential behavior with a short time component of ∼2 ps and a long time component spanning ∼9 ps to 14 ps. The TCM- vibrational probe reports a significantly faster relaxation of ILs compared to those observed previously using linear vibrational probes, such as thiocyanate and selenocyanate. Our results indicate a rapid relaxation of the local ion-cage structure embedding the vibrational probe in the ILs. The faster relaxation suggests that the lifetime of the local ion-cage structure decreases in the presence of TCM- in the ILs. Linear IR spectroscopic results show that the hydrogen-bonding interaction between TCM- and imidazolium cations in ILs is much weaker. Shorter ion-cage lifetimes together with weaker hydrogen-bonding interactions account for the low shear viscosity of TCM- based ILs compared to commonly used ILs. In addition, this study demonstrates that TCM- can be used as a potential vibrational reporter to study the structure and dynamics of ILs and other molecular systems.
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Affiliation(s)
- Biswajit Guchhait
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Clara A Tibbetts
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Kathryn M Tracy
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Bradley M Luther
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Amber T Krummel
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
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23
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Li X, Zhou D, Hao H, Chen H, Weng Y, Bian H. Vibrational Relaxation Dynamics of a Semiconductor Copper(I) Thiocyanate (CuSCN) Film as a Hole-Transporting Layer. J Phys Chem Lett 2020; 11:548-555. [PMID: 31884795 DOI: 10.1021/acs.jpclett.9b03480] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The semiconductor CuSCN film, which is typically used as the hole-transporting layer (HTL) in solar cell studies, has been investigated by Fourier transform infrared (FTIR) spectroscopy and ultrafast transient infrared (IR) spectroscopy. A sharp peak at 2175 cm-1 corresponding to the CN vibrational stretching mode in CuSCN was observed, and the peak frequency remained unchanged by varying the thickness of the CuSCN thin film. Vibrational relaxation measurements showed that the 0-1 and 1-2 transitions of CN stretching can be observed at 2175 and 2140 cm-1, respectively. The heat-induced absorption and bleaching peaks (2167 and 2175 cm-1) can be clearly seen at a waiting time of 40 ps. The vibrational relaxation of the CN stretching mode determined from the 1-2 transition exhibited a biexponential decay with time constants of 7.4 ± 0.5 (90%) and 158 ± 50 ps (10%). Importantly, the abnormal anisotropy decay of the CN stretching mode in the CuSCN thin film was also observed for the first time. A detailed analysis showed that the distinct anisotropy decay curve could be described using a triexponential decay function, which was explained by three different processes: resonance energy transfer (∼8 ps), a thermalization process (∼40 ps), and molecular rotation (∼150 ps). The time scale of the thermalization process caused by the vibrational relaxation in CuSCN is at a time scale of 40 ps, which is important for us to understand the thermally activated charge-transport property of the CuSCN film employed as the HTL. Further UV pump-IR probe measurement revealed that the carrier scattering and relaxation processes in the CuSCN film are strongly associated with the vibrational excitation and relaxation dynamics of the CN stretching mode. It is expected that the fundamental understanding of the vibrational relaxation dynamics of the CuSCN thin film should provide helpful insight to elucidate its role as the HTL in solar cell studies at the molecular level.
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Affiliation(s)
- Xiaoqian Li
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Dexia Zhou
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Hongxing Hao
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Hailong Chen
- Beijing National Laboratory for Condensed Matter Physics, CAS Key Laboratory of Soft Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
| | - Yuxiang Weng
- Beijing National Laboratory for Condensed Matter Physics, CAS Key Laboratory of Soft Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
| | - Hongtao Bian
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
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24
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Floisand DJ, Miller TC, Corcelli SA. Dynamics and Vibrational Spectroscopy of Alcohols in Ionic Liquids: Methanol and Ethanol. J Phys Chem B 2019; 123:8113-8122. [PMID: 31487987 DOI: 10.1021/acs.jpcb.9b07122] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure, dynamics, and vibrational spectroscopy of dilute HOD, methanol, and ethanol in the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][NTf2], ionic liquid (IL) are investigated with molecular dynamics (MD) simulations. The structure of the ILs around the solutes is qualitatively similar, where the OD bond of the deuterated alcohols donates an interaction to an [NTf2] anion and the [emim] cations interact with the oxygen atom of the OD group. The slowest time scale for the reorientational dynamics of the OD bond varied considerably for HOD, methanol, and ethanol (27, 71, and 87 ps, respectively). In contrast, the slowest time scales for spectral diffusion of the OD vibrational frequency were 11 ps for each of the three solutes, which indicates that the dynamics of the IL is relatively unchanged by the presence of the alcohols at dilute concentration. The theoretical results for the reorientational and spectral diffusion dynamics compare favorably with prior two-dimensional infrared (2D IR) spectroscopic measurements.
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Affiliation(s)
- Danyal J Floisand
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , Indiana 46556 , United States
| | - Tierney C Miller
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , Indiana 46556 , United States
| | - Steven A Corcelli
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , Indiana 46556 , United States
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25
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Williams IM, Qasim LN, Tran L, Scott A, Riley K, Dutta S. C-D Vibration at C2 Position of Imidazolium Cation as a Probe of the Ionic Liquid Microenvironment. J Phys Chem A 2019; 123:6342-6349. [PMID: 31257885 DOI: 10.1021/acs.jpca.9b02387] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Unlike molecular solvents, imidazolium-based ionic liquids are entirely made of ions with spatial heterogeneity. There is a need for spectroscopic probes that can assess the microenvironment near the cations of these complex liquids. In this manuscript, we describe simple chemical procedures to label the C2 position of imidazolium cation with a C-D vibrational probe and show, through linear and nonlinear vibrational spectroscopies, that this C-D stretching mode can be a useful analytical tool to assess both the solvent microenvironment and solute-solvent interactions in imidazolium-based ionic liquids from the cation point of view. It is expected that this C-D vibration probe on the cation will lead to the development of innovative experimental strategies that can provide a better understanding of such ionic liquids.
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Affiliation(s)
- Isis Marie Williams
- Department of Chemistry , Xavier University of Louisiana , New Orleans , Louisiana 70125 , United States
| | - Layla N Qasim
- Department of Chemistry , Tulane University , New Orleans , Louisiana 70118 , United States
| | - Ly Tran
- Department of Chemistry , Xavier University of Louisiana , New Orleans , Louisiana 70125 , United States
| | - Asia Scott
- Department of Chemistry , Xavier University of Louisiana , New Orleans , Louisiana 70125 , United States
| | - Kevin Riley
- Department of Chemistry , Xavier University of Louisiana , New Orleans , Louisiana 70125 , United States
| | - Samrat Dutta
- Department of Chemistry , Xavier University of Louisiana , New Orleans , Louisiana 70125 , United States
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26
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Wei Q, Zhang M, Zhou D, Li X, Bian H, Fang Y. Ultrafast Hydrogen Bond Exchanging between Water and Anions in Concentrated Ionic Liquid Aqueous Solutions. J Phys Chem B 2019; 123:4766-4775. [PMID: 31082232 DOI: 10.1021/acs.jpcb.9b03504] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) ionic liquids (ILs) and water as a function of IL concentrations have been investigated by Fourier transform infrared (FTIR) spectroscopy and ultrafast two-dimensional IR (2D IR) spectroscopy. FTIR spectra of the mixtures resolve two different types of water species, one interacting with the BF4- anions and the other associated with bulklike water molecules. These two water species are in a dynamic equilibrium through forming different hydrogen bonding configurations which are separated by more than 100 cm-1 in the IR spectra. The structural dynamics of the IL mixtures are further revealed by monitoring the vibrational relaxation dynamics of the OD stretching group of interfacial water molecules hydrogen bonded to BF4- anions. With the increase of the IL bulk concentration, vibrational population and rotational dynamics of the interfacial water molecules can be described by a biexponential decay function and are strongly dependent on the IL concentrations. Furthermore, the ultrafast hydrogen bond exchanging between water and BF4- anions in the ILs are also measured using 2D IR spectroscopy. The average hydrogen bond exchanging rate is determined to be 19 ± 4 ps, which is around 3 times slower than that in the NaBF4 electrolyte aqueous solution. The much slower hydrogen bond exchanging rate indicates that the local structure of ILs and water molecules are strongly mediated by the steric effect of the cationic group in the ILs, which is proposed to be responsible for the formation of the heterogeneous structure in the IL mixtures. By using SCN- as the anionic probe, the structural inhomogeneity in the IL solutions can be confirmed from the distinct rotational dynamics of the SCN-, which is segregated from the rotational dynamics of water molecules in the IL mixtures.
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Affiliation(s)
- Qianshun Wei
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Miaomiao Zhang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Dexia Zhou
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Xiaoqian Li
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Hongtao Bian
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| | - Yu Fang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
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27
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Daly CA, Allison C, Corcelli SA. Modeling Carbon Dioxide Vibrational Frequencies in Ionic Liquids: IV. Temperature Dependence. J Phys Chem B 2019; 123:3797-3803. [PMID: 30943725 DOI: 10.1021/acs.jpcb.9b01863] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In previous papers in the series, the vibrational spectroscopy of CO2 in ionic liquids (ILs) was investigated at ambient conditions. Here, we extend these studies to understand the temperature dependence of the structure, dynamics, and thermodynamics of CO2 in the 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], IL. Using spectroscopic mapping techniques, the infrared absorption spectrum of the CO2 asymmetric stretch mode is simulated at a number of temperatures, and the results are found to be consistent with similar experimental studies. Structural correlation functions are used to reveal the thermodynamics of complete CO2 solvent cage breakdown. The enthalpy and entropy of activation for solvent cage reorganization are found to be 6.9 and 7.6 (kcal/mol)/K, respectively, and these values are similar to the those for spectral, orientational, and translational diffusion. Caging times for CO2 are calculated, and it is shown that the short time dynamics of CO2 are unaffected by temperature, even though the long-time dynamics are highly sensitive to temperature.
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Affiliation(s)
- Clyde A Daly
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , Indiana 46656 , United States
| | - Cecelia Allison
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , Indiana 46656 , United States
| | - Steven A Corcelli
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , Indiana 46656 , United States
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28
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Hunger J, Roy S, Grechko M, Bonn M. Dynamics of Dicyanamide in Ionic Liquids is Dominated by Local Interactions. J Phys Chem B 2019; 123:1831-1839. [PMID: 30717596 PMCID: PMC6398149 DOI: 10.1021/acs.jpcb.8b10849] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
![]()
The
dynamics of probe molecules is commonly used to investigate
the structural dynamics of room-temperature ionic liquids; however,
the extent to which this dynamics reflects the dynamics of the ionic
liquids or is probe specific has remained debated. Here, we explore
to what extent the vibrational and rotational dynamics of the dicyanamide
anion, a common ionic liquid anion, correlates with the structural
relaxation of ionic liquids. We use polarization-resolved, ultrafast
infrared spectroscopy to probe the temperature- and probe-concentration-dependent
dynamics of samples with small amounts of 1-ethyl-3-methylimidazolium
([emim]+) dicyanamide ([DCA]−) dissolved
in four [emim]+-based ionic liquids with tetrafluoroborate
([BF4]−), bis(trifluoromethylsulfonyl)imide
([NTf2]−), ethylsufate ([EtSO4]−), and triflate ([OTf]−) as
anions. The transient spectra after broad-band excitation at 2000–2300
cm–1, resonant with the symmetric and antisymmetric
C≡N stretching vibrations, initially contain oscillatory signatures
due to the vibrational coherence between both modes. Vibrational population
relaxation occurs on two distinct time scales, ∼6–7
and ∼15–20 ps. The vibrational dynamics is rather insensitive
to the details of the ionic liquid anion and temperature, except for
the slow vibrational relaxation component. The decay of the excitation
anisotropy, a measure of the rotational dynamics of [DCA]−, markedly depends on temperature, and the obtained decay time exhibits
an activation energy of ∼15–21 kJ/mol. Remarkably, neither
the rotation time nor the activation energy can be simply explained
by the variation of the macroscopic viscosity. Hence, our results
suggest that the dynamics of dicyanamide is only in part representative
of the ionic liquid structural dynamics. Rather, the dynamics of the
probe anion seems to be determined by the specific interaction of
[DCA]− with the ionic liquid’s ions for the
class of [emim]+-based ionic liquids studied here.
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Affiliation(s)
- Johannes Hunger
- Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany
| | - Soham Roy
- Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany.,Graduate School Materials Science in Mainz , Staudingerweg 9 , 55128 Mainz , Germany
| | - Maksim Grechko
- Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany
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29
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Zhou D, Wei Q, Wang S, Li X, Bian H. Counterion Effect on Vibrational Relaxation and the Rotational Dynamics of Interfacial Water and an Anionic Vibrational Probe in the Confined Reverse Micelles Environment. J Phys Chem Lett 2019; 10:176-182. [PMID: 30582817 DOI: 10.1021/acs.jpclett.8b03389] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Vibrational relaxation and the rotational dynamics of water molecules encapsulated in reverse micelles (RMs) have been investigated by ultrafast infrared (IR) spectroscopy and two-dimensional IR (2D IR) spectroscopy. By changing the counterion of the hydrophilic headgroup in the RMs formed by Aerosol-OT (AOT) from Na+ to K+, Cs+ and Ca2+, we could determine the specific counterion effects on the rotational dynamics of water molecules. The orientational relaxation time constant of water decreases in the order Ca2+ > Na+ > K+ > Cs+. The SCN- anionic probe and counterion can form ion pairs at the interfacial region of the RMs. The rotational dynamics of SCN- anion significantly decreases because of the synergistic effects of confinement and the surface interactions in the interfacial region of the RMs. The results can provide a new understanding of the cationic Hofmeister effect at the molecular level observed in biological studies.
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Affiliation(s)
- Dexia Zhou
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an , 710119 , China
| | - Qianshun Wei
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an , 710119 , China
| | - Shuyan Wang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an , 710119 , China
| | - Xiaoqian Li
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an , 710119 , China
| | - Hongtao Bian
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an , 710119 , China
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30
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Wei Q, Zhou D, Li X, Chen Y, Bian H. Structural Dynamics of Dimethyl Sulfoxide Aqueous Solutions Investigated by Ultrafast Infrared Spectroscopy: Using Thiocyanate Anion as a Local Vibrational Probe. J Phys Chem B 2018; 122:12131-12138. [DOI: 10.1021/acs.jpcb.8b10058] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Qianshun Wei
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - Dexia Zhou
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - Xiaoqian Li
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - Yuwan Chen
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
| | - Hongtao Bian
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, China
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31
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Brinzer T, Daly CA, Allison C, Garrett-Roe S, Corcelli SA. Modeling Carbon Dioxide Vibrational Frequencies in Ionic Liquids: III. Dynamics and Spectroscopy. J Phys Chem B 2018; 122:8931-8942. [PMID: 30160958 DOI: 10.1021/acs.jpcb.8b05659] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In recent years, interest in carbon capture and sequestration has led to numerous investigations of the ability of ionic liquids to act as recyclable CO2-sorbent materials. Herein, we investigate the structure and dynamics of a model physisorbing ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1Im][PF6]), from the perspective of CO2 using two-dimensional (2D) IR spectroscopy and molecular dynamics simulations. A direct comparison of experimentally measured and calculated 2D IR line shapes confirms the validity of the simulations and spectroscopic calculations. Taken together, the simulations and experiments reveal new insights into the interactions of a CO2 solute with the surrounding ionic liquid and how these interactions manifest in the 2D IR spectra. In particular, higher CO2 asymmetric stretch vibrational frequencies are associated with softer, less populated solvent cages and lower frequencies are associated with tighter, more highly populated solvent cages. The CO2 interacts most strongly with the anions, and these interactions persist for more than 1 ns. The second strongest interactions are with the imidazolium cation ring that last 100 ps, and the weakest interactions are with the cation butyl tail that persist for 10 ps. The principal contributors to spectral diffusion of the CO2 asymmetric stretch vibrational frequency due to the dynamical evolution of the solvent are through Lennard-Jones interactions at short times and electrostatics at long times.
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Affiliation(s)
- Thomas Brinzer
- Department of Chemistry , University of Pittsburgh , 219 Parkman Avenue , Pittsburgh , Pennsylvania 15260 , United States.,Pittsburgh Quantum Institute , University of Pittsburgh , 3943 O'Hara Street , Pittsburgh , Pennsylvania 15260 , United States
| | - Clyde A Daly
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46656 , United States
| | - Cecelia Allison
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46656 , United States
| | - Sean Garrett-Roe
- Department of Chemistry , University of Pittsburgh , 219 Parkman Avenue , Pittsburgh , Pennsylvania 15260 , United States.,Pittsburgh Quantum Institute , University of Pittsburgh , 3943 O'Hara Street , Pittsburgh , Pennsylvania 15260 , United States
| | - Steven A Corcelli
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46656 , United States
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32
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Jo S, Park SW, Noh C, Jung Y. Computer simulation study of differential capacitance and charging mechanism in graphene supercapacitors: Effects of cyano-group in ionic liquids. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2018.07.126] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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33
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Nishida J, Breen JP, Lindquist KP, Umeyama D, Karunadasa HI, Fayer MD. Dynamically Disordered Lattice in a Layered Pb-I-SCN Perovskite Thin Film Probed by Two-Dimensional Infrared Spectroscopy. J Am Chem Soc 2018; 140:9882-9890. [PMID: 30024160 DOI: 10.1021/jacs.8b03787] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The dynamically flexible lattices in lead halide perovskites may play important roles in extending carrier recombination lifetime in 3D perovskite solar-cell absorbers and in exciton self-trapping in 2D perovskite white-light phosphors. Two-dimensional infrared (2D IR) spectroscopy was applied to study a recently reported Pb-I-SCN layered perovskite. The Pb-I-SCN perovskite was spin-coated on a SiO2 surface as a thin film, with a thickness of ∼100 nm, where the S12CN- anions were isotopically diluted with the ratio of S12CN:S13CN = 5:95 to avoid vibrational coupling and excitation transfer between adjacent SCN- anions. The 12CN stretch mode of the minor S12CN- component was the principal vibrational probe that reported on the structural evolution through 2D IR spectroscopy. Spectral diffusion was observed with a time constant of 4.1 ± 0.3 ps. Spectral diffusion arises from small structural changes that result in sampling of frequencies within the distribution of frequencies comprising the inhomogeneously broadened infrared absorption band. These transitions among discrete local structures are distinct from oscillatory phonon motions of the lattice. To accurately evaluate the structural dynamics through measurement of spectral diffusion, the vibrational coupling between adjacent SCN- anions had to be carefully treated. Although the inorganic layers of typical 2D perovskites are structurally isolated from each other, the 2D IR data demonstrated that the layers of the Pb-I-SCN perovskite are vibrationally coupled. When both S12CN- and S13CN- were pumped simultaneously, cross-peaks between S12CN and S13CN vibrations and an oscillating 2D band shape of the S12CN- vibration were observed. Both observables demonstrate vibrational coupling between the closest SCN- anions, which reside in different inorganic layers. The thin films and the isotopic dilution produced exceedingly small vibrational echo signal fields; measurements were made possible using the near-Brewster's angle reflection pump-probe geometry.
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Affiliation(s)
- Jun Nishida
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - John P Breen
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Kurt P Lindquist
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Daiki Umeyama
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Hemamala I Karunadasa
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Michael D Fayer
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
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34
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Daly CA, Brinzer T, Allison C, Garrett-Roe S, Corcelli SA. Enthalpic Driving Force for the Selective Absorption of CO 2 by an Ionic Liquid. J Phys Chem Lett 2018; 9:1393-1397. [PMID: 29504771 DOI: 10.1021/acs.jpclett.8b00347] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Molecular dynamics (MD) simulations validated against two-dimensional infrared (2D-IR) measurements of CO2 in an imidazolium-based ionic liquid have revealed new insights into the mechanism of CO2 solvation. The first solvation shell around CO2 has a distinctly quadrupolar structure, with strong negative charge density around the CO2 carbon atom and positive charge density near the CO2 oxygen atoms. When CO2 is modeled without atomic charges (thus removing its strong quadrupole moment), its solvation shell weakens and changes significantly into a structure that is similar to that of N2 in the same liquid. The solvation shell of CO2 evolves more quickly when its quadrupole is removed, and we find evidence that solvent cage dynamics is measured by 2D-IR spectroscopy. We also find that the solvent cage evolution of N2 is similar to that of CO2 with no atomic charges, implying that the weaker quadrupole of N2 is responsible for its higher diffusion and lower absorption in ionic liquids.
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Affiliation(s)
- Clyde A Daly
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46656 , United States
| | - Thomas Brinzer
- Department of Chemistry , University of Pittsburgh , 219 Parkman Avenue , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , University of Pittsburgh , 3943 O'Hara Street , Pittsburgh , Pennsylvania 15260 , United States
| | - Cecelia Allison
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46656 , United States
| | - Sean Garrett-Roe
- Department of Chemistry , University of Pittsburgh , 219 Parkman Avenue , Pittsburgh , Pennsylvania 15260 , United States
- Pittsburgh Quantum Institute , University of Pittsburgh , 3943 O'Hara Street , Pittsburgh , Pennsylvania 15260 , United States
| | - Steven A Corcelli
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46656 , United States
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35
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Zang J, Feng M, Zhao J, Wang J. Micellar and bicontinuous microemulsion structures show different solute–solvent interactions: a case study using ultrafast nonlinear infrared spectroscopy. Phys Chem Chem Phys 2018; 20:19938-19949. [DOI: 10.1039/c8cp01024b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Using aqueous and organic probes to simultaneously explore the structural dynamics of reverse micellar and bicontinuous microemulsion structures.
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Affiliation(s)
- Jinger Zang
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
| | - Minjun Feng
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
| | - Juan Zhao
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
| | - Jianping Wang
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
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36
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Ren Z, Kelly J, Gunathilaka CP, Brinzer T, Dutta S, Johnson CA, Mitra S, Garrett-Roe S. Ultrafast dynamics of ionic liquids in colloidal dispersion. Phys Chem Chem Phys 2017; 19:32526-32535. [PMID: 29188825 DOI: 10.1039/c7cp04441k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquid (IL)-surfactant complexes have significance both in applications and fundamental research, but their underlying dynamics are not well understood. We apply polarization-controlled two-dimensional infrared spectroscopy (2D-IR) to study the dynamics of [BMIM][SCN]/surfactant/solvent model systems. We examine the effect of the choice of surfactants and solvent, and the IL-to-surfactant ratio (W-value), with a detailed analysis of the orientation and structural dynamics of each system. Different surfactants create very different environments for the entrapped ILs, ranging from a semi-static micro-environment to a fluxional environment that evolves even faster than the bulk IL. The oil-phase also clearly affects the microscopic dynamics. The anisotropy decay for entrapped ILs completes within 10 ps, which is similar to free thiocyanate ion in water, while a significant reorientation-induced spectral diffusion (RISD) effect is observed. The entrapped ionic liquid are highly dynamic for all W-values, and no core-shell structure is observed. We hypothesize that, instead of an ionic liquid-reverse micelle (IL-RM), the microscopic structure of this system is small colloidal dispersions or pairs of IL and surfactants. A detailed analysis of the polarization-controlled 2D-IR spectra of AOT system reveals a potential ion-exchange mechanism.
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Affiliation(s)
- Zhe Ren
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA 15260, USA.
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37
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Brinzer T, Garrett-Roe S. Temperature and chain length dependence of ultrafast vibrational dynamics of thiocyanate in alkylimidazolium ionic liquids: A random walk on a rugged energy landscape. J Chem Phys 2017; 147:194501. [DOI: 10.1063/1.4991813] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Thomas Brinzer
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Sean Garrett-Roe
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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38
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Garrett-Roe S. Reorientation-induced spectral diffusion of non-isotropic orientation distributions. J Chem Phys 2017; 147:144504. [DOI: 10.1063/1.4993864] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Sean Garrett-Roe
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, USA
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39
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Nishida J, Yan C, Fayer MD. Enhanced nonlinear spectroscopy for monolayers and thin films in near-Brewster’s angle reflection pump-probe geometry. J Chem Phys 2017. [DOI: 10.1063/1.4977508] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Affiliation(s)
- Jun Nishida
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Chang Yan
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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40
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Wang H, Liu M, Zhao Y, Xuan X, Zhao Y, Wang J. Hydrogen bonding mediated ion pairs of some aprotic ionic liquids and their structural transition in aqueous solution. Sci China Chem 2017. [DOI: 10.1007/s11426-016-0389-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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41
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Yamada SA, Bailey HE, Tamimi A, Li C, Fayer MD. Dynamics in a Room-Temperature Ionic Liquid from the Cation Perspective: 2D IR Vibrational Echo Spectroscopy. J Am Chem Soc 2017; 139:2408-2420. [DOI: 10.1021/jacs.6b12011] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Steven A. Yamada
- Department of Chemistry Stanford University, Stanford, California 94305, United States
| | - Heather E. Bailey
- Department of Chemistry Stanford University, Stanford, California 94305, United States
| | - Amr Tamimi
- Department of Chemistry Stanford University, Stanford, California 94305, United States
| | - Chunya Li
- Department of Chemistry Stanford University, Stanford, California 94305, United States
| | - Michael D. Fayer
- Department of Chemistry Stanford University, Stanford, California 94305, United States
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42
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Du L, Geng C, Zhang D, Lan Z, Liu C. Atomic Resolution Insights into the Structural Aggregations and Optical Properties of Neat Imidazolium-Based Ionic Liquids. J Phys Chem B 2016; 120:6721-9. [DOI: 10.1021/acs.jpcb.6b04218] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Likai Du
- Key
Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and
Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, Shandong, P. R. China
- Institute
of Theoretical Chemistry, Shandong University, Jinan 250100, P. R. China
- Hubei
Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan 430070, P. R. China
| | - Cuihuan Geng
- Institute
of Theoretical Chemistry, Shandong University, Jinan 250100, P. R. China
| | - Dongju Zhang
- Institute
of Theoretical Chemistry, Shandong University, Jinan 250100, P. R. China
| | - Zhenggang Lan
- Key
Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and
Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, Shandong, P. R. China
| | - Chengbu Liu
- Institute
of Theoretical Chemistry, Shandong University, Jinan 250100, P. R. China
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43
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Hettige JJ, Araque JC, Kashyap HK, Margulis CJ. Communication: Nanoscale structure of tetradecyltrihexylphosphonium based ionic liquids. J Chem Phys 2016; 144:121102. [DOI: 10.1063/1.4944678] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
| | - Juan C. Araque
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA
| | - Hemant K. Kashyap
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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44
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Tamimi A, Fayer MD. Ionic Liquid Dynamics Measured with 2D IR and IR Pump–Probe Experiments on a Linear Anion and the Influence of Potassium Cations. J Phys Chem B 2016; 120:5842-54. [DOI: 10.1021/acs.jpcb.6b00409] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amr Tamimi
- Department
of Chemistry Stanford University, Stanford, California 94305, United States
| | - Michael D. Fayer
- Department
of Chemistry Stanford University, Stanford, California 94305, United States
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45
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Weber H, Kirchner B. Complex Structural and Dynamical Interplay of Cyano-Based Ionic Liquids. J Phys Chem B 2016; 120:2471-83. [DOI: 10.1021/acs.jpcb.6b00098] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Henry Weber
- Mulliken Center for Theoretical
Chemistry, Universität Bonn, Beringstrasse 4 + 6, D-53115 Bonn, Germany
| | - Barbara Kirchner
- Mulliken Center for Theoretical
Chemistry, Universität Bonn, Beringstrasse 4 + 6, D-53115 Bonn, Germany
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46
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Hack J, Grills DC, Miller JR, Mani T. Identification of Ion-Pair Structures in Solution by Vibrational Stark Effects. J Phys Chem B 2016; 120:1149-57. [PMID: 26807492 DOI: 10.1021/acs.jpcb.5b11893] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ion pairing is a fundamental consideration in many areas of chemistry and has implications in a wide range of sciences and technologies that include batteries and organic photovoltaics. Ions in solution are known to inhabit multiple possible states, including free ions (FI), contact ion pairs (CIP), and solvent-separated ion pairs (SSIP). However, in solutions of organic radicals and nonmetal electrolytes, it is often difficult to distinguish between these states. In the first part of this work, we report evidence for the formation of SSIPs in low-polarity solvents and distinct measurements of CIP, SSIP, and FI, by using the ν(C≡N) infrared (IR) band of a nitrile-substituted fluorene radical anion. Use of time-resolved IR detection following pulse radiolysis allowed us to unambiguously assign the peak of the FI. In the presence of nonmetal electrolytes, two distinct red-shifted peaks were observed and assigned to the CIP and SSIP. The assignments are interpreted in the framework of the vibrational Stark effect (VSE) and are supported by (1) the solvent dependence of ion-pair populations, (2) the observation of a cryptand-separated sodium ion pair that mimics the formation of SSIPs, and (3) electronic structure calculations. In the second part of this work, we show that a blue-shift of the ν(C≡N) IR band due to the VSE can be induced in a nitrile-substituted fluorene radical anion by covalently tethering it to a metal-chelating ligand that forms an intramolecular ion pair upon reduction and complexation with sodium ion. This adds support to the conclusion that the shift in IR absorptions by ion pairing originates from the VSE. These results combined show that we can identify ion-pair structures by using the VSE, including the existence of SSIPs in a low-polarity solvent.
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Affiliation(s)
- John Hack
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States.,Chemical Engineering Department, University of Virginia , 102 Engineers' Way, PO Box 400741, Charlottesville, Virginia 22904-4741, United States
| | - David C Grills
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States
| | - John R Miller
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States
| | - Tomoyasu Mani
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States
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Abstract
Molten salts have been known for centuries and have been used for the extraction of aluminium for over one hundred years and as high temperature fluxes in metal processing. This and other molten salt routes have gradually become more energy efficient and less polluting, but there have been few major breakthroughs. This paper will explore some recent innovations that could lead to substantial reductions in the energy consumed in metal production and in carbon dioxide production. Another way that molten salts can contribute to an energy efficient world is by creating better high temperature fuel cells and novel high temperature batteries, or by acting as the medium that can create novel materials that can find applications in high energy batteries and other energy saving devices, such as capacitors. Carbonate melts can be used to absorb carbon dioxide, which can be converted into C, CO and carbon nanoparticles. Molten salts can also be used to create black silicon that can absorb more sunlight over a wider range of wavelengths. Overall, there are many opportunities to explore for molten salts to play in an efficient, low carbon world.
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Affiliation(s)
- Derek Fray
- Department of Materials Science and Metallurgy
- University of Cambridge
- Cambridge CB3 0FS
- UK
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Dutta S, Ren Z, Brinzer T, Garrett-Roe S. Two-dimensional ultrafast vibrational spectroscopy of azides in ionic liquids reveals solute-specific solvation. Phys Chem Chem Phys 2015; 17:26575-9. [PMID: 26193916 DOI: 10.1039/c5cp02119g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The stereochemistry and the reaction rates of bimolecular nucleophilic substitution reactions involving azides in ionic liquids are governed by solute-solvent interactions. Two-dimensional ultrafast vibrational spectroscopy (2D-IR) shows that the picosecond dynamics of inorganic azides are substantially slower than organic azides in a series of homologous imidazolium ionic liquids. In water, both organic and inorganic azides spectrally diffuse with a ∼2 ps time constant. In the aprotic solvent tetrahydrofuran, both kinds of azides spectrally diffuse on a timescale >5 ps. In ionic liquids, like 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), organic azides spectrally diffuse with a 2-4 ps time constant, and inorganic azides spectrally diffuse with a >40 ps time constant. Such a striking difference suggests that neutral (organic) and charged (inorganic) azides are incorporated in the ionic liquids with different solvation structures.
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Affiliation(s)
- Samrat Dutta
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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Araque JC, Hettige JJ, Margulis CJ. Modern Room Temperature Ionic Liquids, a Simple Guide to Understanding Their Structure and How It May Relate to Dynamics. J Phys Chem B 2015; 119:12727-40. [DOI: 10.1021/acs.jpcb.5b05506] [Citation(s) in RCA: 225] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Juan C. Araque
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Jeevapani J. Hettige
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Claudio J. Margulis
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
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