Molecular structures and normal vibrations of trifluoromethane sulfonate (CF3SO3-) and its lithium ion pairs and aggregates

1994 ◽  
Vol 98 (1) ◽  
pp. 100-110 ◽  
Author(s):  
Weiwei Huang ◽  
Roger Frech ◽  
Ralph A. Wheeler
Keyword(s):  
Ion Pairs ◽  
Lithium Ion ◽  
Molecular Structures ◽  
Normal Vibrations

scholarly journals Pyr1,xTFSI Ionic Liquids (x = 1–8): A Computational Chemistry Study

2020 ◽  
Vol 10 (23) ◽  
pp. 8552
Author(s):  
Sergio Brutti
Keyword(s):  
Ionic Liquids ◽  
Physicochemical Properties ◽  
Density Functional ◽  
Ion Pairs ◽  
Molecular Size ◽  
Molecular Structures ◽  
Safety Standards ◽  
Oxidation Reduction ◽  
Reduction Stability ◽  
The Impact

Pyrrolidinium-based (Pyr) ionic liquids are a very wide family of molecular species. Pyrrolidinium cations are electrochemically stable in a large potential interval and their molecular size hinders their transport properties. The corresponding ionic liquids with trifluoromethyl sulphonyl imide anions are excellent solvents for lithium/sodium salts and have been demonstrated as electrolytes in aprotic batteries with enhanced safety standards. In this study, the analysis of the physicochemical properties of a homologous series of pyrrolidinium-based ionic liquids with general formula Pyr1,xTFSI (x = 1–8) have been tackled by first principles calculations based on the density functional theory. The molecular structures of isolated ions and ion pairs have been predicted by electronic structure calculations at B3LYP level of theory in vacuum or in simulated solvents. Thermodynamic properties have been calculated to evaluate the ion pairs dissociation and oxidation/reduction stability. This is the first systematic computational analysis of this series of molecules with a specific focus on the impact of the length of the alkyl chain on the pyrrolidinium cation on the overall physicochemical properties of the ion pairs.

scholarly journals Recent Applications of Molecular Structures at Silicon Anode Interfaces

Electrochem ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 664-676
Author(s):  
Chen Fang ◽  
Gao Liu
Keyword(s):  
Surface Engineering ◽  
Strong Dependence ◽  
Lithium Ion ◽  
Structural Diversity ◽  
High Reactivity ◽  
Molecular Structures ◽  
Design Strategies ◽  
Metal Organic ◽  
Si Anode ◽  
Molecular Nanostructures

Silicon (Si) is a promising anode material to realize many-fold higher anode capacity in next-generation lithium-ion batteries (LIBs). Si electrochemistry has strong dependence on the property of the Si interface, and therefore, Si surface engineering has attracted considerable research interest to address the challenges of Si electrodes such as dramatic volume changes and the high reactivity of Si surface. Molecular nanostructures, including metal–organic frameworks (MOFs), covalent–organic frameworks (COFs) and monolayers, have been employed in recent years to decorate or functionalize Si anode surfaces to improve their electrochemical performance. These materials have the advantages of facile preparation, nanoscale controllability and structural diversity, and thus could be utilized as versatile platforms for Si surface modification. This review aims to summarize the recent applications of MOFs, COFs and monolayers for Si anode development. The functionalities and common design strategies of these molecular structures are demonstrated.

A Raman spectral study of solvation and ion association in the systems LiAsF6/CH3CO2CH3 and LiAsF6/HCO2CH3

1991 ◽  
Vol 69 (11) ◽  
pp. 1766-1773 ◽  
Author(s):  
Zhongyi Deng ◽  
Donald E. Irish
Keyword(s):  
Methyl Acetate ◽  
Methyl Formate ◽  
Ion Pairs ◽  
Lithium Ion ◽  
Ion Association ◽  
Ion Solvation ◽  
Lithium Cation ◽  
Different Types ◽  
Raman Spectral ◽  
Contact Ion Pairs

The structure of the solvated lithium cation in methyl acetate (MA) solutions has been investigated using Raman spectroscopy. Two bands at 844 and 864 cm−1 have been assigned to two different types of MA: the former is from the bulk solvent and the latter arises from MA molecules solvating the lithium cation. From measurement of changes in intensity of these bands with increasing salt concentration a solvation number of four for Li+ in MA has been inferred. Changes in the Raman bands at ca. 1740 cm−1 suggest that solvation occurs through the carbonyl group. Evidence for contact ion pairing between Li+ and AsF6− is also presented. An equilibrium between solvent-shared ion pairs and contact ion pairs is proposed for which an equilibrium constant is estimated. The system LiAsF6/methyl formate (MF) is similar in structure. Key words: Raman, ion pair formation, lithium and hexafluoroarsenate ions, methyl acetate and formate, lithium ion solvation.

scholarly journals The absorption spectra and photochemistry of poly­atomic molecules containing alkyl radicals - V—Vibration frequencies and structure

1937 ◽  
Vol 160 (903) ◽  
pp. 539-562 ◽  
Keyword(s):  
Force Field ◽  
Degrees Of Freedom ◽  
A Priori ◽  
Ultra Violet ◽  
Force Constants ◽  
Molecular Structures ◽  
Vibration Frequencies ◽  
Complex Molecules ◽  
Normal Vibrations ◽  
Alkyl Radicals

One of the most important properties of a molecule is its ability to vibrate. A complete knowledge of the normal vibrations of a polyatomic molecule not only provides valuable indications of its structure, but also may eventually be of value in elucidating the mechanism of reactions in which the molecule takes part, for it is largely among such vibrational degrees of freedom that energies of activation may be stored. The vibration frequencies of molecules are usually determined by spectroscopic methods, and considerations based on known Raman, infra-red, or ultra-violet spectral data often make it possible not only to determine their magnitudes but also to assign observed vibration frequencies to the specific vibrational types. It is, however, also possible, provided some knowledge of the force field existing in a molecule is assumed, to calculate the normal vibration frequencies of molecules, and at the same time to deduce the directions of the atomic amplitudes. Such calculations (Bjerrum 1914; Dennison 1926; Yates 1931; Radakowicz 1930, 1932; Lechner 1932; Howard and Wilson 1934; Sutherland 1936; Howard 1935; Sutherland and Dennison 1935) often serve to test previous empirical assignments, and may also help in deciding or confirming the molecular structures. If the vibration frequencies of a molecule are known from experimental data, both in regard to magnitude and assignment, we can, conversely, calculate the properties of the force field existing in the molecule, this being customarily expressed by the magnitudes of the various “force constants”. We might then, a priori at least, expect to be able to use these deduced force constants in calculating the vibration frequencies of more complex molecules of the same type and involving similar linkages. An example of this procedure is discussed in the present paper, and the extent of its limitations is revealed.

Carbon acidity. 71. The indicator scale of lithium ion pairs in tetrahydrofuran

1986 ◽  
Vol 108 (22) ◽  
pp. 7016-7022 ◽  
Author(s):  
Scott. Gronert ◽  
Andrew. Streitwieser
Keyword(s):  
Ion Pairs ◽  
Lithium Ion

Effet de cation sur la réactivité ambidente des anions: la nette tendance à la O-alkylation manifestée par les énolates de lithium de composés β-dicarbonylés

1980 ◽  
Vol 58 (8) ◽  
pp. 786-793 ◽  
Author(s):  
P. Sarthou ◽  
G. Bram ◽  
F. Guibe
Keyword(s):  
Ion Pairs ◽  
Lithium Ion ◽  
Intrinsic Property ◽  
Alkyl Halides ◽  
Alkyl Sulfonates ◽  
Lithium Enolates ◽  
Leaving Group ◽  
Nucleophilic Reactivity ◽  
Specific Reactivity ◽  
Marked Tendency

The study of the specific reactivity of the ion pairs of alkaline enolates of β-dicarbonyl compounds shows that the lithium enolates, in spite of their characteristically strong enolate–cation interactions display, especially when compared to sodium enolates, a marked tendency towards O-alkylation. This strong O-/C-nucleophilicity of the lithium ion pairs is not very sensitive to changes in medium polarity (from THF or DME to DMF) but depends on the nature of the alkylating agent, being enhanced with moderately electrophilic alkyl sulfonates or sulfate but lessened with alkyl halides or with very electrophilic sulfonates (triflate). It is suggested that the lithium enolate tendency towards O-alkylation is partly the result of a Li+ – leaving group interaction (especially in the case of the sulfonates) and partly an intrinsic property of the enolate–lithium ion pair; this latter property is discussed in terms of the respective solvation abilities towards cations of the C- and O-alkylation transition states.Some of our results about the nucleophilic reactivity of ion pairs in DMF are at variance with previous reports in the literature. The origin of the discrepancy is discussed.

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