Taft Parameters Research Articles

Coupling Electron Transfer Reactions of Quinones with Grotthuss Proton Transport of Concentrated Hydrogen-Bonded Electrolytes

Concentrated Hydrogen Bonded Electrolytes (CoHBEs) such as deep eutectic solvents and ionic liquids have been studied for redox flow batteries. The CoHBEs approach has advantages for large-scale energy storage in flow batteries due to its potentially high redox reactant solubility, large electrochemical stability window, low volatility, and the ability to be made of non-toxic and non-corrosive materials. However, they are often viscous and thus transport of ions and reactants are hindered. Protic Concentrated Hydrogen Bonded Electrolytes (P-CoHBEs) are structured electrolytes that facilitate ionic conductivity through Grotthuss type proton transport, and thus decoupling ionic conductivity from electrolyte viscosity. Imidazoles protonated with an acid is an example of a P-CoHBEs. Ideally, coupling a proton coupled electron transfer redox couple with a P-CoHBE will be useful for storing energy in a flow battery. In this research, we studied the charge transfer mechanism and kinetics of 9,10-anthraquinone (AQ) in a P-CoHBE composed of levulinic acid (LA) and 1H-Imidazole (Im) by electroanalytical techniques. The details of the experiments, the measurement results, and interpretation of data will be described in this presentation. The electrochemical behavior of AQ was found to be sensitive to the LA:Im composition where the hydrogen bonding and speciation were effectively varied, thus directly impacting the diffusivity of AQ. The La:Im composition also affected the proton-coupled electron transfer mechanism and under certain conditions the 2-electron transfer of AQ⇌AQ-⇌ AQ2- was observed to occur at a single potential at -0.91 V vs. Fc/Fc+. This suggests tunability of the hydrogen network for efficient and reversible PCET reactions based on P-CoHBEs’ component pKa values and Kamlet Taft parameters. By innovatively decoupling proton conductivity from viscosity through the potential exploitation of the Grotthuss mechanism, our research opens new avenues for enhancing ion transport efficiency in flow batteries and lays the groundwork for designing protic P-CoHBEs that optimize the hydrogen network for quick and reversible PCET reactions on quinones.

Explicable Machine Learning for Predicting High-Efficiency Lignocellulose Pretreatment Solvents Based on Kamlet–Taft and Polarity Parameters

Explicable Machine Learning for Predicting High-Efficiency Lignocellulose Pretreatment Solvents Based on Kamlet–Taft and Polarity Parameters

Solvent Replacement Strategies for Processing Pharmaceuticals and Bio-Related Compounds—A Review

An overview of solvent replacement strategies shows that there is great progress in green chemistry for replacing hazardous di-polar aprotic solvents, such as N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), and 1,4-dioxane (DI), used in processing active industrial ingredients (APIs). In synthetic chemistry, alcohols, carbonates, ethers, eucalyptol, glycols, furans, ketones, cycloalkanones, lactones, pyrrolidinone or solvent mixtures, 2-methyl tetrahydrofuran in methanol, HCl in cyclopentyl methyl ether, or trifluoroacetic acid in propylene carbonate or surfactant water (no organic solvents) are suggested replacement solvents. For the replacement of dichloromethane (DCM) used in chromatography, ethyl acetate ethanol or 2-propanol in heptanes, with or without acetic acid or ammonium hydroxide additives, are suggested, along with methanol acetic acid in ethyl acetate or methyl tert-butyl ether, ethyl acetate in ethanol in cyclohexane, CO2-ethyl acetate, CO2-methanol, CO2-acetone, and CO2-isopropanol. Supercritical CO2 (scCO2) can be used to replace many organic solvents used in processing materials from natural sources. Vegetable, drupe, legume, and seed oils used as co-extractants (mixed with substrate before extraction) can be used to replace the typical organic co-solvents (ethanol, acetone) used in scCO2 extraction. Mixed solvents consisting of a hydrogen bond donor (HBD) solvent and a hydrogen bond acceptor (HBA) are not addressed in GSK or CHEM21 solvent replacement guides. Published data for 100 water-soluble and water-insoluble APIs in mono-solvents show polarity ranges appropriate for the processing of APIs with mixed solvents. When water is used, possible HBA candidate solvents are acetone, acetic acid, acetonitrile, ethanol, methanol, 2-methyl tetrahydrofuran, 2,2,5,5-tetramethyloxolane, dimethylisosorbide, Cyrene, Cygnet 0.0, or diformylxylose. When alcohol is used, possible HBA candidates are cyclopentanone, esters, lactone, eucalytol, MeSesamol, or diformylxylose. HBA—HBA mixed solvents, such as Cyrene—Cygnet 0.0, could provide interesting new combinations. Solubility parameters, Reichardt polarity, Kamlet—Taft parameters, and linear solvation energy relationships provide practical ways for identifying mixed solvents applicable to API systems.

Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis

Solvation properties are key for understanding the interactions between solvents and solutes, making them critical for optimizing chemical synthesis and biochemical applications. Designable solvents for targeted optimization of these end-uses could, therefore, play a big role in the future of the relevant industries. The tailorable nature of protic ionic liquids (PILs) as designable solvents makes them ideal candidates. By alteration of their constituent structural groups, their solvation properties can be tuned as required. The solvation properties are determined by the polar and non-polar interactions of the PIL, but they remain relatively unknown for PILs as compared to aprotic ILs and their characterization is non-trivial. Here, we use solvatochromic dyes as probe molecules to investigate the solvation properties of nine previously uncharacterized alkyl- and dialkylammonium PILs. These properties include the Kamlet–Aboud–Taft (KAT) parameters: π* (dipolarity/polarizability), α (H-bond acidity) and β (H-bond basicity), along with the ET(30) scale (electrophilicity/polarizability). We then used molecular dynamics simulations to calculate the radial distribution functions (RDF) of 21 PILs, which were correlated to their solvation properties and liquid nanostructure. It was identified that the hydroxyl groups on the PIL cation increase α, π* and ET(30), and correspondingly increase the cation–anion distance in their RDF plots. The hydroxyl group, therefore, reduces the strength of the ionic interaction but increases the polarizability of the ions. An increase in the alkyl chain length on the cation led to a decrease in the distances between cations, while also increasing the β value. The effect of the anion on the PIL solvation properties was found to be variable, with the nitrate anion greatly increasing π*, α and anion–anion distances. The research presented herein advances the understanding of PIL structure–property relationships while also showcasing the complimentary use of molecular dynamics simulations and solvatochromic analysis together.

Effective Recognition of Lithium Salt in (Choline Chloride: Glycerol) Deep Eutectic Solvent by Reichardt’s Betaine Dye 33

Deep eutectic solvents (DESs) have emerged as novel alternatives to common solvents and VOCs. Their employment as electrolytes in batteries has been an area of intense research. In this context, understanding changes in the physicochemical properties of DESs in the presence of Li salts becomes of utmost importance. Solvatochromic probes have the potential to gauge such changes. It is reported herein that one such UV–vis molecular absorbance probe, Reichardt’s betaine dye 33, effectively manifests changes taking place in a DES Glyceline composed of H-bond accepting salt choline chloride and H-bond donor glycerol in a 1:2 molar ratio, as salt LiCl is added. The lowest energy intramolecular charge–transfer absorbance band of this dye exhibits a 17 nm hypsochromic shift as up to 3.0 molal LiCl is added to Glyceline. The estimated ETN parameter shows a linear increase with the LiCl mole fraction. Spectroscopic responses of betaine dye 33, N,N-diethyl-4-nitroaniline and 4-nitroaniline are used to assess empirical Kamlet–Taft parameters of dipolarity/polarizability (π*), H-bond-donating acidity (α) and H-bond-accepting basicity (β) as a function of LiCl concentration in Glyceline. LiCl addition to Glyceline results in an increase in α and no change in π* and β. It is proposed that the added lithium interacts with the oxygen of the –OH functionalities on the glycerol rendering of the solvent with increased H-bond-donating acidity. It is observed that pyrene, a popular fluorescence probe of solvent polarity, does respond to the addition of LiCl to Glyceline, however, the change in pyrene response starts to become noticeable only at higher LiCl concentrations (mLiCl ≥ 1.5 m). Reichardt’s betaine dye is found to be highly sensitive and versatile in gauging the physicochemical properties of DESs in the presence of LiCl.

Investigating the effect of mono di carboxylic acids as hydrogen bond donor on solvation of copper in choline chloride-based deep eutectic solvents

Deep eutectic solvents (DESs) are green alternatives to highly acidic solvents or ionic liquids (ILs). The flexible complexation properties of eutectic solvents open their scope as a prospective dissolution medium for metal extraction. The present study investigates the range of monocarboxylic acids-choline chloride (Monocarboxy A-ChCl) and dicarboxylic acid-choline chloride (Dicarboxy A-ChCl) DESs as solvent media for copper oxide dissolution with a discussion on physical properties and their effect on dissolution. Thermal stability, freezing point, Kamlet Taft parameter, density, and viscosity of Carboxy A-ChCl DESs were experimentally determined.The density of Carboxy A-ChCl DESs follows the trend: FA-ChCl < Acetic A-ChCl < OA-ChCl < MA-ChCl < CA-ChCl. The viscosity of Monocarboxy A-ChCl was observed to be lesser than Dicaboxy A-ChCl DESs. The polarity of Monocarboxy A-ChCl was observed to be in the range of 1.2–0.8, while Dicarboxy A-ChCl, polarity was greater than 1. Further, the effect of hydrogen bond donors (HBD), hydrogen bond acceptors (HBA), KFT parameters, viscosity, fukui function of HBD, reaction time and temperature affecting the dissolution of Cu are elaborated in detail. Most dependant to least dependent parameters with respect to dissolution is recognized and some crucial conclusions were put together. Formic acid: Choline chloride (FA-ChCl) DES indicated the highest copper dissolution in the range > 106 ppm. Copper dissolution from ionic CuO to low polar Monocarboxy A-ChCl DESs was higher than in high polar Dicarboxy A-ChCl DESs. DFT calculation reveals that Formic Acid (FA) has the highest fukui functions compared to other carboxylic acids, which is directly reflected in the higher solubility of copper oxides. Additionally, the effect of reaction time and temperature on CuO dissolution in best-performing FA-ChCl DES was studied, 75 °C, 27 h, 100 °C, 18 h were chosen as the optimum time and temperature for maximum dissolution of Cu. The results cover important parameters of Carboxy A-ChCl DES, which could be helpful in metal extraction applications.

A Study of Abraham’s Effective Hydrogen Bond Acidity and Polarity/Polarizability Parameters, A and S, Using Computationally Derived Molecular Properties

AbstractAbraham’s hydrogen bond donor and polarity/polarizability parameters, A and S, respectively, are correlated with molecular properties derived from computational chemistry. The analyses show that A, like Kamlet and Taaft’s α, correlates only with the charge on the most positive hydrogen atom of the molecule but that there are marked steric effects. In contrast, S correlates with the molecular dipole moment, the partial charge on the most negative atom in the molecule and with the polarizability of single ring aromatic compounds but not those of aliphatic compounds. These results are compared with those for corresponding Kamlet and Taft parameters, α and π* and Reichardt’s ET(30) and discussed in terms of the experimental methods used to determine the parameters.

Solvent Effects and Metal Ion Recognition in Several Azulenyl-Vinyl-Oxazolones

The spectral properties of several azulene-oxazolone derivatives containing a phenyloxazolone moiety linked to a substituted azulene ring via a C=C double bond were studied in different solvents of varying polarity. The solvatochromism and the ability of azulene-oxazolone derivatives to recognize heavy metal ions were investigated. In order to estimate the contribution of the non-specific and specific solute–solvent interactions, multiple linear regression analysis using Kamlet–Taft, Catalan and Laurence parameters was applied. These azulene derivatives demonstrate positive solvatochromism. The methyl and isopropyl substituents at the seven-membered azulene ring determine the highest red shifts of the absorption maxima of these azulenyl-vinyl-oxazolones. According to Catalan and Laurence models, the solvent polarizability is a more significant parameter in describing the solvatochromic properties of the azulene-oxazolone derivatives. The azulene-oxazolone compounds under study showed a good response to heavy metal cations (Cd2+, Hg2+, Cu2+ and Pb2+).

Multiscale molecular simulations for the solvation of lignin in ionic liquids

Lignin, the second most abundant biopolymer found in nature, has emerged as a potential source of sustainable fuels, chemicals, and materials. Finding suitable solvents, as well as technologies for efficient and affordable lignin dissolution and depolymerization, are major obstacles in the conversion of lignin to value-added products. Certain ionic liquids (ILs) are capable of dissolving and depolymerizing lignin but designing and developing an effective IL for lignin dissolution remains quite challenging. To address this issue, the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) model was used to screen 5670 ILs by computing logarithmic activity coefficients (ln(γ)) and excess enthalpies (HE) of lignin, respectively. Based on the COSMO-RS computed thermodynamic properties (ln(γ) and HE) of lignin, anions such as acetate, methyl carbonate, octanoate, glycinate, alaninate, and lysinate in combination with cations like tetraalkylammonium, tetraalkylphosphonium, and pyridinium are predicted to be suitable solvents for lignin dissolution. The dissolution properties such as interaction energy between anion and cation, viscosity, Hansen solubility parameters, dissociation constants, and Kamlet–Taft parameters of selected ILs were evaluated to assess their propensity for lignin dissolution. Furthermore, molecular dynamics (MD) simulations were performed to understand the structural and dynamic properties of tetrabutylammonium [TBA]+-based ILs and lignin mixtures and to shed light on the mechanisms involved in lignin dissolution. MD simulation results suggested [TBA]+-based ILs have the potential to dissolve lignin because of their higher contact probability and interaction energies with lignin when compared to cholinium lysinate.

Heuristic Computational Model for Predicting Lignin Solubility in Tailored Organic Solvents

Lignin is a random heteropolymer that has been extensively studied as a renewable source of aromatic precursors for high-value chemicals, biofuels, and bioplastics. A key challenge in lignin valorization is the structural and compositional heterogeneity of lignin feedstocks. Solvent-based approaches are commonly used to fractionate lignin to reduce this heterogeneity, but solvent selection can be challenging due to variability in lignin composition. In this work, we developed computational methods to predict good and poor organic solvents as a function of lignin composition. We analyzed 28 different linear pentamer structures, 18 from known libraries and 10 hypothetical polymers, and calculated their activity coefficients in 50 different organic solvents by using the conductor-like screening model for realistic solvents. We used these data to train a regression model that enabled the extensive investigation of the impact of solvent and monolignol compositions on predicted lignin solubility. The exhaustive exploration of solubility trends using model predictions revealed sets of solvents, identified using Kamlet–Taft parameters, that are predicted to promote lignin dissolution regardless of lignin composition. We further identified solvents expected to selectively isolate lignin fractions enriched in certain subunits. These results establish heuristic guidelines for solvent selection that can be used to tailor fractionation processes for lignin feedstocks of distinct composition or to design new processes that isolate fractions with higher proportions of selected subunits.

Characterizing the Properties of Anion-Binding Bis(cyclopeptides) with Solvent-Independent Energy Increments

The binding energies of 121 complexes between anions and bis(cyclopeptides) differing in the structure and the number of linking units between the two cyclopeptide rings were analyzed. These Gibbs free energies were obtained in earlier work for different anions, under different conditions, and with different methods. The multiparametric analysis of a subset of 42 binding energies afforded linear relationships that allowed the relatively reliable estimation of the iodide and sulfate affinity of three structurally related bis(cyclopeptides) in water/methanol and water/acetonitrile mixtures at different solvent compositions. Three parameters were required to achieve a satisfactory correlation, namely, the Gibbs free energy of transferring the respective anion from water into the solvent mixture in which complex stability was determined, and the Kamlet–Taft parameters α and β. Based on these relationships, the anion affinities of the other bis(cyclopeptides) were evaluated, giving rise to a set of energy increments that allow quantifying the effects of the linker structure or the nature of the anion on binding affinity relative to the reference system.

Synthesis, characterization and solvatochromic behaviour of new water-soluble 8-hydroxy-3,6-disulphonaphthyl azohydroxynaphthalenes

A series of five tetracyclic mono azo dyes based on the diazotization of 1-amino-8-hydroxynaphthalene-3,6-disulphonic acid and subsequent coupling with substituted (un)sulphonated naphthalene derivatives have been synthesized. The chemical structures of the dyes were established using UV–visible, IR, NMR as well as mass spectrometry. Based on the number of sulphonic acid and other hydrophilic groups they contain, the compounds showed varying extent of water solubility. Spectroscopic characterization revealed the existence of azo-hydrazone tautomerism and the influence of the structures of solvating solvents on the equilibrium. Statistical analysis of single, dual and multiparametric equations of Kamlet Abboud and Taft parameters showed that solvent polarity was the most significant contributor to the observed spectral patterns of the dyes in pure solvents. The compounds could find useful applications as solvatochromic probes, food and drug colour additives.

Delineating solvation behaviour and molecular interactions within ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate + ethylene glycol monomethyl ether solutions

Cosolvent-modified ionic liquid (IL)-based binary mixtures have been used in several chemical applications. Therefore, the molecular-level understanding of these binary mixtures is of utmost necessity to enhance their utility in applications in several fields. This work involves the spectroscopic study of the binary mixture of the IL 1‑butyl‑3-methylimidazolium tetrafluoroborate ([bmim][BF4]) and ethylene glycol monomethyl ether (EGME) using several polarity-based absorbence and fluorescence probes (Reichardt's dye 33, pyrene, and 1-pyrene carboxaldehyde) and the microviscosity probe 9-(2,2-dicyanovinyl) julolidine (DCVJ). The behaviour of these probes hints at the synergistic behaviour of the IL–EGME mixtures. The Kamlet–Taft parameters have also been calculated and provide an understanding of the solute–solvent and/or solvent–solvent interactions. Further, the dynamic viscosity and Fourier transform infrared spectroscopy (FTIR) results suggest strong hydrogen bonding between the IL and EGME molecules. The preferential solvation model also indicates the formation of a new entity due to solvent–solvent interactions.

The Influence of Monomer Structure on the Properties of Ionogels Obtained by Thiol–Ene Photopolymerization

The influence of ene and thiol monomer structure on the mechanical and electrochemical properties of thiol–ene polymeric ionogels were investigated. Ionogels were obtained in situ by thiol–ene photopolymerization of 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATT), 2,4,6-triallyloxy-1,3,5-triazine (TAT), diallyl phthalate (DAP), and glyoxal bis(diallyl acetal) (GBDA) used as enes and trimethylolpropane tris(3-mercaptopropionate) (TMPTP), pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), and pentaerythritol tetrakis(3-mercaptobutyrate) (PETMB) used as thiols in 70 wt.% of ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImNTf2). The mechanical strength of ionogels was studied by puncture resistance and ionic conductivity by electrochemical impedance spectroscopy. The course of photopolymerization by photo-DSC method (differential scanning calorimetry) as well as characterization of compositions and its components (by IR and UV spectroscopy-Kamlet–Taft parameters) were also studied. The resulting ionogels were opaque, with phase separation, which resulted from the dispersion mechanism of polymerization. The mechanical and conductive properties of the obtained materials were found to be largely dependent on the monomer structure. Ionogels based on triazine monomers TAT and TATT were characterized by higher mechanical strength, while those based on aliphatic GBDA had the highest conductivity. These parameters are strongly related to the structure of the polymer matrix, which is in the form of connected spheres. The conductivity of ionogels was high, in the range of 3.5–5.1 mS∙cm−1.

Using COSMO-RS to Predict Solvatochromic Parameters for Deep Eutectic Solvents

The development of novel green solvents demands the knowledge of their properties, such as polarity, which can be described through solvatochromic parameters. However, while these are available for a wide range of conventional solvents, there is a lack of data for the emergent ones. Considering the need for such data, predictive models to estimate the Kamlet–Taft (K–T) parameters for deep eutectic solvents (DES) are developed here. The models, based on the conductor-like screening model for real solvents (COSMO-RS) descriptors, were initially developed and tested for 175 organic solvents to validate the applicability of the proposed approach. This approach was then extended for DES, which were classified into two categories, acids and nonacids. The developed equations showed a very good performance for all three K–T parameters, and this is the first work to propose models for all K–T parameters for DES. Moreover, a comparison between polarity data of DES and organic compounds showed that DES, rather than replace common solvents, can extend their range of polarities, reinforcing their designer solvent ability.

Sodium Hexanoate and Dodecanoate Salt-Based Eutectic Solvents: Density, Viscosity, and Kamlet–Taft Parameters

Eutectic solvents (ESs) are a relatively new class of solvents that have been arousing a lot of attention due to their easy preparation and great tunability of their thermophysical properties, which has been granting their application in a wide range of areas. The aim of this work is to present a new ES based on the mixture of an organic sodium salt, sodium hexanoate and dodecanoate, and a long alkyl chain carboxylic acid, octanoic, nonanoic, and decanoic acids, and to infer about the effect of introducing a sodium atom. The solid–liquid phase diagrams of these new sodium salt-based ES were determined to evaluate the liquid window where they can be confidently used as solvents. Other important properties of solvents have also been studied, and in particular, density and viscosity, at atmospheric pressure and in the temperature range between 293.15 and 353.15 K, were measured. In addition, the polarity of these new sodium salt-based deep eutectic solvents (DESs) was evaluated in terms of the Kamlet–Taft α, β, and π* and ETN parameters. The obtained results were compared with those of other commonly used hydrophilic and hydrophobic DESs and conclusions were taken.

Solubility of Carbon Dioxide in Deep Eutectic Solvents Based on 3-Amino-1-Propanol and Tetraalkylammonium Salts at Low Pressure.

Deep eutectic solvents (DESs) became an object of a great interest as an alternative to ionic liquids (ILs) and commonly used in CO2 capture amine solutions. In the present study, five different DESs based on 3-amino-1-propanol as physical-chemical CO2 absorbents were used. The composition was chosen in order to estimate the effects of hydrogen bond acceptor:hydrogen bond donor (HBA:HBD) molar ratio, anion type and length of alkyl chain of composing salt. The Fourier Transform Infrared (FTIR) spectroscopy was used to confirm chemical reaction. The solubility of CO2 was measured at low pressures up to 170 kPa at the temperature range of 293–318 K. Viscosity, polarity and Kamlet–Taft parameters were determined in order to estimate the dependences of the parameters and the CO2 capacity. CO2 uptake was observed to improve with decreasing molar ratio of hydrogen bond donor. Comparing the CO2 capacity of [TBAC]-based DESs, at the approximate pressure of 50 kPa, it was observed that the capacity increased in the following order of molar ratios—1:8 < 1:6 < 1:4 and a decrease in molar ratio from 1:8 to 1:4 resulted in about a 100% increase of capacity. Compared to [TBAC][AP] DESs, the [TEAC][AP] 1:4 and [TBAB][AP] 1:4 exhibited higher CO2 uptake, though the best results were obtained for [TBAB][AP].

Theoretical Study of the Reactivity of Phenyl Radicals Toward Enol Acetates

Arylation reactions are an important class of reactions and allow the synthesis of natural and synthetic products. Despite the efficient, but high cost and toxic methodologies involving transition metals, radical arylations have gained importance after the advent of photoredox catalysis. Arylation of enol acetates is an important tool for obtaining aryl ketones but the scope of the reaction is limited to the pattern of substitution at phenyl radical and α-carbon of the enol. Theoretical calculations ((U)BHandHLYP/6-311G**) show that the polar effect is the key factor in this reaction. A good correlation of calculated rate constants with field effect explained why phenyl radicals with electron-withdrawing groups react faster toward enol acetate. The presence of alkyl groups at α carbon at the enol showed some influence of enthalpic effect but strong influence of steric effect, evidenced by great correlations with Taft and Charton parameters. Finally, substitution at β carbon showed no significant effect at reaction rates.

Spectral Study of Two Carbanion Mono-substituted 4�-phenyl-1,2,4-triazol-1-ium Phenacylids in Binary Protic Solvents

The visible electronic absorption band of two 4�-phenyl-1,2,4-triazol-1-ium phenacylids was studied in two binary solvents: water (1) + ethanol (2) and water (1) + methanol (2) with variable content in water. The nature and the contribution of the intermolecular interactions to the spectral shifts in ternary solutions of the studied ylids were estimated based on the Kamlet Taft parameters (�*, a and a) previously measured by Buhvestov and all. The influence of the universal and specific interactions on the visible electronic band of the studied ylids depends on the water concentration in binary solvent. At small water concentrations in binary solvent, the hydrogen complexes of the type ylid-alcohol are predominant, while at high water concentrations, the complexes made by hydrogen bonds between water and ylid molecules prevail. The difference between the energies corresponding to molecular pairs of the types: ylid-water and ylid-alcohol was estimated based on the statistic cell model of the ternary solutions.

Electron paramagnetic resonance studies of the chelate-based ionic liquid in different solvents

The electron paramagnetic resonance spectra of the chelate-based ionic liquid [C10mim][Cu(F6-acac)3] in different solvents have been obtained at 120 K. It was found that the values of the 63Cu hyperfine coupling constants (AIL) of [C10mim][Cu(F6-acac)3] in molecular solvents were from 116 to 180 Gauss. Moreover, the AIL values in general ionic liquids are more complicated, and two sets of peaks can often be observed in their electron paramagnetic resonance spectra. Based on the Kamlet–Taft parameters, relative permittivity, the experimental results were discussed in terms of solvation effect and coordination of the solvents.