Picosecond Dynamics of Molecular Entities in Lithium Salt Solutions in Dimethyl Sulfoxide, Propylene Carbonate, and Dimethyl Carbonate

2018 ◽  
Vol 63 (3) ◽  
pp. 245 ◽  
Author(s):  
M. I. Gorobets ◽  
S. A. Kirillov
Keyword(s):  
Dimethyl Sulfoxide ◽  
Propylene Carbonate ◽  
Molten Salts ◽  
Dimethyl Carbonate ◽  
Lithium Salt ◽  
Ion Pairs ◽  
Lithium Salts ◽  
Strong Interactions ◽  
Solvent Molecules ◽  
Contact Ion Pairs

An analysis of the Raman spectra of the solutions of lithium salts in dimethyl sulfoxide, propylene carbonate, and dimethyl carbonate in a concentration range from diluted solutions to the mixtures of molten solvates with salts has been performed in terms of the dynamics, specifically, the dephasing (тv) and modulation (тw) times of all molecular entities present in solutions are determined and analyzed. It has been found that, in the picosecond time domain, the dephasing and modulation in solvent molecules hydrogen-bonded with an anion and/or solvating a cation are slower than in free solvent molecules. In solvent separated ion pairs, both тv and тw are much longer than in solvated anions, thus indicating the strong interactions between anions and their surrounding. In contact ion pairs, тv are great, whereas тw appear close to those for free anions. This reflects that the structure of the liquid tends to the structure of molten salts.

scholarly journals Speciation in Solutions of Lithium Salts in Dimethyl Sulfoxide, Propylene Carbonate, and Dimethyl Carbonate from Raman Data: A Minireview

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
M. I. Gorobets ◽  
M. B. Ataev ◽  
M. M. Gafurov ◽  
S. A. Kirillov
Keyword(s):  
Dimethyl Sulfoxide ◽  
Propylene Carbonate ◽  
Dimethyl Carbonate ◽  
Weak Interactions ◽  
Lithium Salts ◽  
Strong Interactions ◽  
Carbonate Solutions ◽  
Order Of Magnitude ◽  
Anions And Cations ◽  
Solvent Molecules

Our recent Raman studies of cation and anion solvation and ion pairing in solutions of lithium salts in dimethyl sulfoxide, propylene carbonate, and dimethyl carbonate are briefly overviewed. Special attention is paid to differences in our and existing data and concepts. As follows from our results, cation solvation numbers in solutions are low (~2) and disagree with previous measurements. This discrepancy is shown to arise from correct accounting for dimerization, hydrogen bonding, and conformation equilibria in the solvents disregarded in early studies. Another disputable question touches upon the absence of free ions in solutions of lithium salts in carbonate solvents and the statement that the charge transfer in carbonate solutions is caused by SSIPs. Direct proofs of the nature of charge carriers in the solvents studied have been obtained by means of analyses of vibrational dynamics. It has been found that collision times for free anions are short and evidence weak interactions between anions and solvent molecules. In SSIPs, collision times are an order of magnitude longer thus signifying strong interactions between anions and cations. In CIPs, collision times become shorter than in SSIPs reflecting the transformation of the structure of concentrated solutions to that of molten salts.

scholarly journals When spectroscopy fails: The measurement of ion pairing

2006 ◽  
Vol 78 (8) ◽  
pp. 1571-1586 ◽  
Author(s):  
Glenn Hefter
Keyword(s):  
Metal Ion ◽  
Chemical Speciation ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Spectroscopic Techniques ◽  
Association Equilibria ◽  
Solvent Molecules ◽  
Contact Ion Pairs

Spectroscopic techniques such as UV/vis, NMR, and Raman are powerful tools for the investigation of chemical speciation in solution. However, it is not widely recognized that such techniques do not always provide reliable information about ion association equilibria. Specifically, spectroscopic measurements do not in general produce thermodynamically meaningful association constants for non-contact ion pairs, where the ions are separated by one or more solvent molecules. Such systems can only be properly quantified by techniques such as dielectric or ultrasonic relaxation, which can detect all ion-pair types (or equilibria), or by traditional thermodynamic methods, which detect the overall level of association. Various types of quantitative data are presented for metal ion/sulfate systems in aqueous solution that demonstrate the inadequacy of the major spectroscopic techniques for the investigation of systems that involve solvent-separated ion pairs. The implications for ion association equilibria in general are briefly discussed.

Preparation and crystal structure determination of triphenylmethanide cesium · 1.5 dimethoxyethane and of phenothiazine cesium diglyme

1998 ◽  
Vol 213 (3) ◽  
Author(s):  
H. Bock ◽  
T. Hauck ◽  
C. Näther
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Ion Pairs ◽  
Polymer Chains ◽  
Polymeric Chains ◽  
Moisture Sensitive ◽  
Counter Cation ◽  
Solvent Molecules ◽  
Contact Ion Pairs

AbstractReaction of triphenylmethane with cesium metal in dimethoxyethane (DME) or of phenothiazine in diglyme yields two organometallic cesium compounds as extremly air and moisture sensitive single crystals. In triphenylmethanide cesium · 1.5 DME, the counter cations form two structurally different contact ion pairs to symmetry-related triphenylmethanide anions and are solvated in addition by two crystallographically independent ether solvent molecules, which partly connect the resulting polymeric chains. In phenothiazine cesium diglyme, each counter cation is surrounded by three symmetry-related phenothiazine anions and one diglyme molecule predominantly via their oxygen, nitrogen and sulfur centers and again infinite polymer chains are formed. All structural results are discussed based on literature data of analogous complexes.

Vibrational spectra of anhydrous lithium perchlorate in crystalline and molten states

1969 ◽  
Vol 22 (3) ◽  
pp. 499 ◽  
Author(s):  
WH Leong ◽  
DW James
Keyword(s):  
Molten Salts ◽  
Ion Pairs ◽  
Lithium Perchlorate ◽  
Frequency Region ◽  
Infrared And Raman Spectra ◽  
Molten State ◽  
Infrared And Raman Spectroscopy ◽  
Degenerate Modes ◽  
Contact Ion Pairs ◽  
Crystalline Symmetry

Anhydrous lithium perchlorate has been examined in the crystalline and molten state by infrared and Raman spectroscopy. In the crystalline phase all degenerate modes are split but the Raman and infrared spectra are essentially identical in the internal frequency region. In the molten state the spectra are more simple but no coincidences exist between infrared and Raman spectra. The spectra are interpreted in terms of a crystalline symmetry perturbation for both the solid and molten salts. The symmetry of the perturbing field is shown to change in going from the solid to the melt. An explanation of the melt spectra in terms of contact ion pairs is considered and dismissed. Observed vibrational frequencies and assignments are given.

Ion Pairing and Dielectric Decrement in Glycosaminoglycan Brushes

2020 ◽  
Author(s):  
James Sterling ◽  
Wenjuan Jiang ◽  
Wesley M. Botello-Smith ◽  
Yun L. Luo
Keyword(s):  
Molecular Dynamics ◽  
Ion Pairs ◽  
Mean Field ◽  
Salt Bridge ◽  
Ion Pairing ◽  
Donnan Potential ◽  
Mean Field Models ◽  
Ion Exclusion ◽  
Dynamics Simulations ◽  
Contact Ion Pairs

Molecular dynamics simulations of hyaluronic acid and heparin brushes are presented that show important effects of ion-pairing, water dielectric decrease, and co-ion exclusion. Results show equilibria with electroneutrality attained through screening and pairing of brush anionic charges by cations. Most surprising is the reversal of the Donnan potential that would be expected based on electrostatic Boltzmann partitioning alone. Water dielectric decrement within the brush domain is also associated with Born hydration-driven cation exclusion from the brush. We observe that the primary partition energy attracting cations to attain brush electroneutrality is the ion-pairing or salt-bridge energy associated with cation-sulfate and cation-carboxylate solvent-separated and contact ion pairs. Potassium and sodium pairing to glycosaminoglycan carboxylates and sulfates consistently show similar abundance of contact-pairing and solvent-separated pairing. In these crowded macromolecular brushes, ion-pairing, Born-hydration, and electrostatic potential energies all contribute to attain electroneutrality and should therefore contribute in mean-field models to accurately represent brush electrostatics.

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