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Citrate precursors of copper, nickel and cobalt oxides, namely Cu(C6H7O7)2·5H2O, Ni(C6H7O7)2·2.5H2O and CoC6H6O7·6H2O, have been synthesized from solutions with metal to citric acid ratio of 1:2, their thermal decomposition has been studied, and decomposition products have been analyzed. It has been found that the Cu salt loses water and then forms acidic aconitate and acidic itaconate, which then transforms to normal itaconate and further to CuO. The Ni salt dehydrates and decomposes directly to normal itaconates and then to NiO mixed with Ni metal. The Co salt dehydrates and then transforms to normal aconitate, normal itaconate and to Co3O4 containing CoO. While the oxides in question form crystallites of 15–25 nm size with pores of around 3–4 nm in radii, their morphology differs significantly. CuO particles are nanosized. Unlike them, NiO and Co3O4 develop aggregates of approx. 300–500 nm size. Similarities and differences in decomposition processes and morphology of the target oxides are analyzed and discussed, and possible improvements of the citric acid-aided route are suggested. It is shown, in particular, that the formation of metallic Ni and CoO is predetermined by thermodynamics of redox processes involving oxygen and carbon monoxide obtained by the decomposition of the organic part of precursors.

Phase diagrams of lithium salt systems in dimethyl sulfoxide, propylene carbonate and dimethyl carbonate have been obtained and conductivity measurements have been performed in the concentration range up to 0.25 mole fraction of a salt. The shape of the phase diagrams has been analyzed thermodynamically and the following order of anions for decreasing association of salts with DMSO at cLiX = 0.2 has been suggested, ClO4− > CF3SO3− > BF4− > NO3−. The eutectic-type phase diagrams of the LiClO4-PC and LiClO4-DMC systems correspond to ideal, non-interacting solutions. The conductivity isotherms for the DMSO solutions at cLiX = 0.2 are arranged in the order of increasing conductivity as CF3SO3− c LiClO 4 = 0.5–1 mole fraction of the salt, the order of solvents for increasing conductivity is DMC

Raman study of cation and anion solvation in dimethyl sulfoxide, propylene carbonate and dimethyl carbonate solutions of six lithium salts has been performed in the concentration range from 0.05 to 0.25 molar fraction of a salt. The dependences of the amount of the solvent particles involved in dimerization, hydrogen bonding, and solvation have been determined, and the mean solvation numbers have been found. It is concluded that in all solutions studied, notwithstanding the differences in the physical properties of the solvent and in the structure of the anion, both the lithium cation and the anion solvation equilibria are quantitatively similar. In all cases, solvation numbers of cations are close to two and do not vary with the growth of concentration. In particular, in molten LiX·4S solvates, LiS 4 + entities expected from the phase diagrams do not exist. It has been found that for the solvent molecules in dimers and in solvation spheres, non-coincidences between vibrational frequencies of isotropic and anisotropic lines, Δ ν NCE = ν aniso − ν iso are of opposite signs signifying that the mutual orientation of molecules is different. In all systems studied, solvation numbers of anions decrease if the salt content is growing and are close to four in concentrated solutions. These striking similarities in the structure and concentration of solvated entities clearly signify that solvation phenomena have no decisive importance in determining the properties of salt systems.

Ionic equilibria in the LiBF4-dimethyl sulfoxide (DMSO) system were studied by Raman spectroscopy at 50°C at salt concentrations of 0.05–0.25 mole fractions. The spectral signals of hydrogen bonds between the DMSO molecules and the fluoroborate ions were found. The concentrations of the monomer and dimer DMSO molecules and DMSO molecules in the solvation sphere of the lithium cation; free solvent molecules and those in the solvation sphere of the fluoroborate ion; free anions, ion pairs separated by the solvent, and contact ion pairs were determined.

The Raman spectra of the mixtures containing the low-temperature ionic liquid ethylmethylimidazolinium bis(trifluoromethanesulfonyl)imide (EMIIm), the salt component lithium bis(trifluoromethylesulfonyl)-imide (LiIm), and the aprotic solvent ethylene carbonate (EC) are studied. It is found that the addition of the lithium salt to the ionic liquid results in the formation of ion pairs or more complex cation-anion aggregates. Dilution of these systems with ethylene carbonate leads to the solvation of lithium ions.

The phase diagrams, isotherms of the electrical conductivity, Raman spectra, and time correlation functions of vibrational dephasing are studied for the LiN(CF3SO2)2-(CH3)2SO2 system, which is promising for use as an electrolyte in medium-temperature lithium-ion batteries. The phase diagram of this system contains a broad supercooled region. It is shown that the concentration dependences of the electrical conductivity are typical for solutions of strong electrolytes. The Raman spectra and the time correlation functions of vibrational dephasing for the anion and the solvent indicate that in the supercooling range, cations are weakly solvated by solvent molecules and form ion pairs.

Raman scattering spectra of dimethyl sulfoxide (DMSO) are studied in the area of the line corresponding to symmetric CSC stretching vibrations of the molecule. It is established that this line is composed of a low-frequency component that corresponds to the vibrations of monomeric molecules and a high-frequency component that corresponds to the vibrations of DMSO dimers. Values of self-association equilibrium constants K a varying in range from 0.20 (23°C) to 0.081 (100°C) are obtained. Since the intensities of the respective components of the line contour are proportional to the compound’s concentrations, the enthalpy of DMSO self-association (ΔH = −11.7 ± 0.9 kJ/mol) is determined from the temperature dependences.

Raman spectroscopy has been used to investigate picosecond vibrational dynamics of the molecular glass-former phenyl salicylate (salol). The study has concentrated on the elucidation and comparison of molecular dynamics of salol subjected to different local environments, namely in bulk, in a dilute CCl4 solution, and under spatial confinement in nanoporous sol–gel glasses. Contrary to most of the previous picosecond dynamics studies performed by means of Raman line profile analysis, we have employed in this paper a novel approach that enables the extraction of valuable short-time dynamics information through spectra fitting in the frequency domain. As a result, strongly overlapping vibrational lines can be put in focus. The analysis has shown a systematic dependence of vibrational relaxation on the local environment around a salol molecule. The magnitude of the vibrational relaxation time τV decreases in the sequence dilute solution→bulk liquid→confined liquid, indicating the modification of interactions ...

The picosecond dynamics of molten alkali halides is discussed, and the low-frequency Raman spectra of molten LiCl, CsCl, and the LiCl–CsCl eutectic are fitted to the model enabling to obtain the times of vibrational dephasing, τV and vibrational frequency modulation τω. In terms of the Wilmshurst criterion [J. Chem. Phys. 39, 1779 (1963)] and using the data of NMR studies and molecular dynamics simulations, a conclusion is drawn that molten alkali halides cannot contain long-lived stable complexes with lifetimes greater than 10−8 s. The low-frequency Raman spectra of molten alkali halides and their mixtures probe the presence of instantaneous spatial configurations of MXn−n+1 type, where M+ is the alkali metal cation and X− is the halide anion existing in melts during the time intervals equal to the time of duration of collision of oppositely charged ions τd, which is less than 0.5 ps. This time is sufficient to a collision complex to execute several (at least one) vibrations. Vibrational dephasing and mo...

In this article we present the first quantitative estimates of the spectroscopically active part of the interaction potential in molten complex chlorides based on dephasing studies. We have selected the molten salt systems containing quasispherical complex MCl4−2 anions (M=Mn+2 and Zn+2) and performed the study of their ν1(A1) isotropic Raman line profiles as a function of the temperature and concentration. We have analyzed the form of the time correlation function of vibrational dephasing and determined the type of modulation events, which cause the line broadening processes in these systems; these are found to be purely discrete Markovian. Within the formalism of the purely discrete Markovian modulation, we have made a judgement about spectroscopically active interactions in these systems. Interionic potential in complex chlorides is dominated by the attraction forces, which depend on the interparticle distance r as r−4, and by repulsion of the r−7-type.

A fitting method is described which enables one to model real line profiles intermediate between Lorentzian and Gaussian by an analytical function which has an analytical counterpart in the time domain. The applications of this method comprise: (1) finding time correlation functions and correlation times by fits in the frequency domain without Fourier transforms; and (2) the decomposition of overlap lines obtaining dynamic parameters at the same time.

Distinguishing features of spectroscopy of interparticle interactions in ionic liquids are pointed out. Studies of interactions and picosecond dynamics in molten salts using this approach are reviewed. Similarities and differences between molecular and ionic liquids which manifest themselves in spectroscopic experiments are compared and discussed.

Dimethyl sulfoxide (DMSO) has been known for almost 150 years, but its properties as a solvent and reaction medium are far from being understood. In particular, association equilibriums in liquid DMSO have been characterized in just four papers, and the enthalpy of its self-association is unknown. The aims of this paper are to study self-association equilibriums in neat liquid DMSO at various temperatures by means of Raman spectroscopy, to find the enthalpy of self-association, and to solve the problem of hydrogen bonding in this liquid. Time correlation functions of vibrational dephasing and reorientation of coexisting monomers and dimers studied by the C-S-C and C-H symmetric vibrations indicate that external perturbations and vibrational and reorientational dynamics of these particles occur on different time scales. No signatures of H-bonding in DMSO are found. The association constants vary from 0.20 L mol(-1) (23 °C) to 0.081 L mol(-1) (100 °C). Their temperature dependence gives the enthalpy of association of DMSO as -11.7 ± 0.9 kJ mol(-1).

In terms of the theory which describes the instantaneous frequency shifts in liquids as a purely discrete Markovian process, an approximate analytical expression for the time correlation functions of vibrational dephasing is given, and its fit to experimental data is tested. A comparison with the (non-Markovian) stretched exponential model is made. Within the two theories, the static correlation function being transformed by molecular motion are shown to tend to the same Kubo limiting low, but the Markovian process tends from above and non-Markovian from below.

A quick method of determining the parameters of a stretched exponential fit to an experimental time correlation function of vibrational dephasing is proposed and tested.

Predominant solvation of activated complex is shown to be characteristic for chemical and electrochemical reactions in molten salts.

The usual assumption that the reorientational and vibrational motions of the molecules under study are statistically uncorrelated and that the vibrational band profiles in IR, isotropic and anisotropic Raman are identical for the same vibrational mode leads to contradictory results in studies of molten salt dynamics. The conclusion was made that inconsistency of these data may be eliminated when the coupling of vibrational and rotational dephasing is taken into account.

The most obvious consequence of the concept of aromaticity is the common confidence that in aromatic compounds, bond lengths do not alternate and are between typical to the single and double ones. However, in 1994, performing crystal structure investigations of substituted pyridines and their salts, Krygowski and co-workers have discovered a very surprising angular group induced bond alteration (AGIBA) effect: It appears that some angular substituents, like methoxy or nitrozo groups, can induce bond alternation in aromatic rings. Crystal studies do not allow one to operate with liquids that are more common in organic chemistry. This paper presents the first possible evidence of spectroscopic manifestations of the AGIBA effect. Raman spectra of the liquid toluene are analyzed. It is found that instead of being single, the line corresponding to the ring breathing vibrations is clearly split by 1.0–1.4 cm−1, thus indicating the presence of two (cis- and trans-) AGIBA isomers. The energy difference between these isomers estimated in temperature dependent Raman studies is found equal to 6.68 kJ mol−1. The low-wavenumber line therefore corresponds to the cis-AGIBA isomer and the high-wavenumber line to the trans-AGIBA isomer stabilized by the AGIBA effect. Copyright © 2007 John Wiley & Sons, Ltd.

A novel fitting method implemented recently in vibrational spectroscopy of disordered systems is briefly overviewed. It enables modelling of real line profiles intermediate between Lorentzian and Gaussian by an analytical function which has an analytical counterpart in the time domain. Numerous applications of this theoretical approach are discussed.

A method enabling one to separate the contributions of repulsion and attraction forces resulting in frequency non-coincidences in liquids is presented.

Polarization measurements in the Raman spectra of molten sodium nitrite have shown that the reorientational line widths of the v1 and v2 bands (both of the A1 symmetry type) of NO2̄ are different. Possible reasons are discussed. Also, the line widths of NO2̄ for various molten nitrites are found to depend on R-4 , the cloasest approach distance in the melt, and on Z, the cation charge number. This dependence agrees with theoretical predictions for the coupling of vibrational and reorientational dephasing caused by ion-dipole interactions.

A comparison of the ESR spectral parameters of 14 N and 15 N nitroxide radicals in various viscous media in the region of rapid rotational motion is presented. It is shown that is viscous media, such as vaseline oil, polymers, etc., the radical reorientation has a complicated nature which cannot be described by a diffusional process with an anisotropic diffusion tensor.

The rates of perchlorate decomposition in various molten salt solvents have been studied. Activation energies of both catalytic and noncatalytic processes are close and the differences between the rates of these two processes are due to the variations of pre-exponential factors.