Hydrogen Bond Acceptor Basicity Research Articles

Preparation and characterization of novel polyols-based DESs and their use in efficient sequestration of radioactive iodine

The utilization of Novel DESs can be greener alternative to traditional organic solvents. In present study, four polyols-based DESs are synthesized and characterized by several techniques. The prepared DESs are used for the efficient capture of hazardous iodine. In present study by simple combination of two readily accessible, economical, and biodegradable components four polyols-based DESs have been prepared. For the creation of these DESs, a hydrogen bond donors (HBDs) (polyols) and hydrogen bond acceptors (HBAs) (BTEAC) are used, which havemelting points far lower than their respective melting points. The developed DESs were investigated for their physicochemical properties such as density, dynamic viscosity. Our results revealed distinct trends in these properties across different DES compositions, highlighting unique molecular interactions and solvation capabilities. The FTIR and NMR characterization study indicated considerable intermolecular interaction between the various component of the DES system. Further, Kamlet-Taft solvatochromic parameters were determined using Nile red dye, and other solvatochromic dyes. For synthesized DESs, the solvatochromic parameters ENT, normalized polarity parameter, π*, polarity / polarizability; β, hydrogen-bond acceptor basicity and α, hydrogen-bond donor acidity, have been determined. The ENT parameters demonstrate that both non-specific and specific interactions play a significant role in solute–solvent interactions. The synthesized DESs have been utilized for the efficient capture of the iodine. The removal efficiency of DES depends upon the mass of the DESs taken and time duration. These findings deepen our understanding of DES behavior and underscore their versatility in diverse industrial and scientific applications.

New approach: Solvent effects of benzaldehyde in aliphatic alcohol solvents with FT-IR spectroscopy and augmented vertex-adjacency matrices

In this study of benzaldehyde (BNZ) in 7 aliphatic alcohol solvents, were undertaken to investigate the solvent/solute interaction with Fouirer Transform Infrared Spectroscopy (FT-IR), BNZ produced carbonyl group stretching vibration frequencies (ν(C=O)1 and ν(C=O)2). In the present paper, ν(C=O)1 and ν(C=O)2 of BNZ are observed and correlated with the solvent acceptor number (AN), dipolarity/polarizability (π*), hydrogen-bond donor acidity (α), hydrogen-bond acceptor basicity (β), solvent polarity parameter [ET(30)], KBM parameter ƒ(ε), boiling point (bp) and the linear solvation energy relationship (LSER) using single and multiple regression analysis. All calculations were performed for ν(C=O)1 and ν(C=O)2 and compared. ν(C=O)1 was believed to correspond to a single hydrogen bonded BNZ-alcohol complex, while ν(C=O)2 was believed to correspond to a multiple hydrogen bonded BNZ-alcohol complex and multiple hydrogen-bonded alcohol molecules. It was seen that LSER equation as multiple regression analysis was better than single regression analysis in explaining solute-solvent interactions due to the higher correlation coefficients obtained. The correlations of a set of the mathematical characteristics of the augmented vertex-adjacency matrices (AV-AM) obtained by the chemical structure of BNZ with solvent parameters and ν(C=O) were investigated. It was determined that the correlation factors (R2 > 0.999) of the multiparameter regression models obtained using the matrix results were higher than the correlation factors (R2 > 0.99) of the LSER equations including solvent parameters.

Spectroscopic study of solvent effects on the electronic absorption spectra of morpholine and its complexes

The electronic absorption spectra of morpholine and its five morpholine complexes have been studied in different solvents of various polarities. The regression and correlation coefficients have been calculated with the SPSS program. Solvation energy relationships were deduced from spectral shifts and correlated with solvent parameters α (solvent hydrogen bond donor acidity), β (solvent hydrogen bond acceptor basicity), and π* (dipolarity/polarizability). The percentage contributions of the calculated solvatochromic parameters show that classic solvation effects play a major role in explaining the spectral shifts in all investigated complexes. The blue shift of [Fe(MOR)3Cl3]·4H2O, [Ni(MOR)4Cl2]·4H2O, and [Cu(MOR)4Cl2]·6H2O complexes is due to the formation of hydrogen bonds, which suggests the stabilization of the ground electronic state compared with the excited state. [CuNi(MOR)2Cl4]·4H2O and [CuZn(MOR)3Cl4]·2H2O are mixed metal complexes that suffer a red shift due to the solute-solvent interactions, which causes stabilization of the excited solute state with increasing solvent polarity. The bands are affected by specific solute-solvent interactions including hydrogen bond donor ability (acidity) and hydrogen bond acceptor ability (basicity) and nonspecific solute-solvent interactions including electromagnetic interaction between the dipole moments of solute and polar solvents.

Synthesis and spectral properties of novel series of fluorene-based azo dyes containing thiazole scaffold: Studying of the solvent and substituent effect on absorption spectra

A novel series of new 2-arylazo-thiazole dyes pendant to fluorene moiety was synthesized. The novel azodyes have been accessed via the reaction of hydrazonoyl halides with the 2-(9H-fluoren-9-ylidene)hydrazine-1-carbothioamide in a simple manner using mild reaction conditions. The structures of the synthesized dyes were elucidated by spectroscopic tools and elemental analyses. The UV visible spectra of the newly synthesized arylazo dyes were recorded in nine different solvents in the region of 300–800 nm. Solvent and substituents effect, as well as the influence of the addition of acid and base on the absorption frequencies of arylazo thiazoles were discussed. To achieve deep understanding about interactions between the synthesized dyes and solvent, Kamlet-Taft and Catalan model have been used for the evaluation of the solvatochromic shifts of the absorption maxima in UV–vis spectra of the azo-hydrazo tautomers of the arylazo thiazole dyes under investigation. The results revealed the great influence of solvent polarizability and hydrogen-bond acceptor basicity parameters in the absorption frequency shifts of the selected synthesized arylazo dyes. The azo-hydrazo tautomeric form was found to depend on the substituents, solvent as well as when varying pH.

Mapping the solute–solvent interactions for the interpretation of the three types of solvatochromism exhibited by phenolate-based dyes

• The solvatochromism of phenolate-based dyes is rationalized from their solute–solvent interactions in solution. • Multiparametric analysis with Catalán’s solvent scales provided a differentiation of the three types of solvatochromism. • Each type of solvatochromism exhibit different sensitivities to solvent properties. • The pass from negative to positive solvatochromism is governed by the increase of the solvent polarizability by the dyes. • Three strategies for controlling the solvatochromism observed by structural modifications of phenolate dyes are presented. We report the correlation between the hydrogen-bond donor acidity SA, the hydrogen-bond acceptor basicity SB, the solvent polarizability SP, and solvent dipolarity SdP with the type of solvatochromism exhibited by phenolates dyes. We use Catalán’s multiparametric regression analysis of three sets of dyes exhibiting negative, inverted, and positive solvatochromism. We show that these three types of behavior can be differentiated by the solute–solvent interaction these dyes established in solution. Negative solvatochromic dyes exhibit a more robust response to SA than SdP, whereas SP is an essential solvent property for positive and inverted solvatochromic dyes. Our results can be rationalized for the sake of the structural features required for a particular kind of solvatochromism to take place; this is illustrated with selected examples where the introduction of atoms with a + M mesomeric effect or the increase in annulation of the dyes, decrease the SA and SdP sensitivity and increase the SP sensitivity of the dyes, and ultimately control the solvatochromism exhibited from a negative to an inverted or from an inverted to positive behavior.

The separation between solvent polarizability and solvent dipolarity: Revisiting the Kamlet-Abraham-Taft model equation

Quantitative structure–property relationships were established using multiple linear regressions to correlate log k values for the heterolysis reaction of 3-bromo-3-ethylpentane using three well-known model equations, the Kamlet-Abraham-Taft (KAT), the Catalán (Cat) and the Laurence (Lau) equations. The a priori exclusion of the hydrogen bond acceptor (HBA) basicity descriptor for all tested models led to similar responses, thus emptying the argument of an alleged use of a non-balanced set of solvents. Concurrently, a new method was devised to split the original Kamlet-Taft π* descriptor into two independent contributions which separately quantify the solvent’s polarizability (DI) and dipolarity (Dip). A modified version of the KAT equation (mKAT) including both DI and Dip, together with the exclusion of the HBA basicity descriptor was applied to five selected solvent-dependent physicochemical processes. Results showed that the mKAT model provided significant improvements over the original KAT model. Additionally, it was shown that the introduction of DI in the truncated KAT equation could lead to misleading or, at best, inconclusive interpretations of solvent effects. Finally, the performance of mKAT model was compared with Catalán’s and Laurence’s model equations in terms of statistical results, relevance of descriptors and gas-phase predictions. In general, these three model equations show very similar outcomes although the mKAT model exhibits an overall better performance.

Spontaneous Isomerization of a Hydroxynaphthalene-Containing Spiropyran in Polar Solvents Enhanced by Hydrogen Bonding Interactions.

The synthesis of spiropyran dyes exhibiting solvent-driven isomerization even in the dark condition is an important subject for the design of optical materials. A conventional synthesis strategy involves the conjugation of indoline moieties with electron-deficient aromatic moieties. Herein, we report that a spiropyran conjugated with a hydroxynaphthalene moiety (1) is a new member exhibiting solvent-driven isomerization, even bearing an electron-donating −OH moiety. The dye exists as a colorless spirocyclic (SP) form in nonpolar media. It, however, shows a blue color in polar media, especially in aqueous media, due to the formation of ring-opened merocyanine (MC) forms, where the isomerization terminates in 10 s even at room temperature. The spontaneous SP → MC isomerization originates from the MC forms stabilized by the highly delocalized π-electrons on the hydroxynaphthalene moiety. The solvation in polar media and the hydrogen bonding interaction with water molecules decrease the ground-state energy of the MC forms, triggering spontaneous isomerization. The dye exhibits two MC absorption bands assigned to the trans–trans–cis (TTC) and cis–trans–cis (CTC) isomers. The absorbance of the CTC band increases more significantly with an increase in the water content, and the increase exhibits a linear relationship with a hydrogen-bond donor acidity of solvents. The phenolate oxygen of the CTC form has larger hydrogen-bond acceptor basicity, resulting in stronger stabilization by the water molecule.

Densities, heat capacities, viscosities, 1H- and 13C-NMR spectra, and solvatochromic parameters of binary mixtures of 1,3-dimethyl-1,3-diazinan-2-one (DMPU) and water

The compound 1,3-dimethyl-1,3-diazinan-2-one (N,N’-dimethylpropyleneurea, DMPU) is a dipolar aprotic solvent with very strong electron-donating abilities but which is much less toxic and less carcinogenic than similar solvents such as the widely used HMPA (hexamethylphosphorictriamide). This paper reports densities and viscosities of the binary mixtures of (DMPU + water) in the temperature range (293.15 to 353.15) K at 5 K intervals, over the whole composition range. Isobaric heat capacities of these mixtures were measured by flow calorimetry at 298.15 K. The 1H- and 13C-NMR spectra as well as the solvatochromic parameters (polarizability, π*, hydrogen-bond acceptor basicity, β, and hydrogen-bond donor acidity, α) of the mixtures were also determined. The densities and viscosities were sensitive to traces of water in the organic-rich region while the heat capacities were not. Excess molar volumes were strongly negative, showing an extremum at mole fraction xDMPU ≈ 0.40. The variation of viscosity with mixture composition was similar to the density with a sharp maximum at xDMPU ≈ 0.35. Apparent molar volumes, Vϕ, of the mixtures show that the water-DMPU interactions have a larger effect on Vϕ of water than on DMPU. While the standard isobaric molar heat capacity of DMPU in water is much higher than that of DMPU itself, the corresponding value for water in DMPU was not much influenced by the presence of DMPU. The 1H-NMR spectra show that the chemical shift of the water protons is more influenced by mixture composition than those of the DMPU protons. A de-shielding of the DMPU carbonyl carbon resonance was observed in the 13C-NMR spectra at low xDMPU, indicative of H-bonding between the water protons and the non-bonding electrons of the carbonyl oxygen.

Solvatochromic correlation analysis of monomolecular SN1/E1 heterolysis reactions of tertiary haloalkanes

A solvatochromic analysis of the reaction of the solvent-dependent heterolysis reaction of tertiary haloalkanes, based on the properties of the solvents used, allows visualizing and interpreting the intermolecular solute/solvent interactions that control these important chemical processes.The results achieved confirm that the rate of these chemical processes increases in a balanced way with an increase in the polarizability, the dipolarity, and the hydrogen-bond donor (HBD) acidity of the solvents, and to a much lesser extent with their their hydrogen-bond acceptor (HBA) basicity. Contrary to what is currently accepted, namely that the rate of these processes is not or is negatively affected by the solvent's HBA basicity (nucleophilicity), we conclude that if it does, it is positively affected. We also conclude that the Gibbs activation energy of the heterolysis of 2-chloro-2-methylpropane (t-BuCl) decreases by the four solvatochromic contributions to the overall intermolecular solute/solvent interactions.

D‐π‐A Molecular Probe to Unveil the Role of Solute‐Solvent Hydrogen Bonding in Solvatochromism, Location Specific Preferential Solvation and Synergistic Effect in Binary Mixtures

AbstractAn azo dye 4‐(p‐Nitrophenylazo) phenol (NPAP) characterized with a donor‐π‐acceptor (D‐π‐A) framework has been used as a molecular probe to study solvatochromic behavior in neat and binary solvent mixtures comprised of chloroform (a hydrogen bond donor; HBD solvent) and a hydrogen bond acceptor (HBA) solvent. The specificity of the probe lies in its inherent characteristics of having a HBD group and a HBA group at two different ends of the conjugated π‐network. UV‐Vis spectroscopic technique is used for the purpose. The probe demonstrates a very expressive reversal in solvatochromic behavior, with the solvatochromic switch at ET(30) of ∼45 kcal mol−1. Multiparametric treatment of the solvatochromic data using SEV technique displays excellent sensitivity of the probe towards HBA basicity, dipolarity and polarizability of the medium with a smaller but significant contribution from HBD acidity and hydrophobicity/apolarity. The event of preferential solvation in the chloroform‐HBA mixture is explained on the basis of specific solute‐solvent interaction through HBD and HBA ability of the solvent components. HBA solvents preferentially solvate the phenolic site while HBD solvents preferentially solvate the nitrobenzene group through complementary hydrogen bonding, which results in an increase in local concentration at specific sites resulting in synergistic preferential solvation. The proposition of site selective PS through molecular recognition is also supported by theoretical studies.

Discovery of Balovaptan, a Vasopressin 1a Receptor Antagonist for the Treatment of Autism Spectrum Disorder.

We recently reported the discovery of a potent, selective, and brain-penetrant V1a receptor antagonist, which was not suitable for full development. Nevertheless, this compound was found to improve surrogates of social behavior in adults with autism spectrum disorder in an exploratory proof-of-mechanism study. Here we describe scaffold hopping that gave rise to triazolobenzodiazepines with improved pharmacokinetic properties. The key to balancing potency and selectivity while minimizing P-gp mediated efflux was fine-tuning of hydrogen bond acceptor basicity. Ascertaining a V1a antagonist specific brain activity pattern by pharmacological magnetic resonance imaging in the rat played a seminal role in guiding optimization efforts, culminating in the discovery of balovaptan (RG7314, RO5285119) 1. In a 12-week clinical phase 2 study in adults with autism spectrum disorder balovaptan demonstrated improvements in Vineland-II Adaptive Behavior Scales, a secondary end point comprising communication, socialization, and daily living skills. Balovaptan entered phase 3 clinical development in August 2018.

Preferential solvation of p-nitroaniline in a binary mixture of chloroform and hydrogen bond acceptor solvents: the role of specific solute-solvent hydrogen bonding.

Preferential solvation of solvatochromic probe p-nitroaniline (PNA) has been studied in binary mixtures of chloroform with different hydrogen bond acceptor (HBA) solvents using the spectroscopic transition energy (ET). Analyses of the solvatochromic shifts of the absorption spectra of PNA in different neat solvents as a function of the solvent polarity parameters reveal the major contribution from the solvent dipolarity/polarizability and HBA basicity in the solvation of PNA. The event of preferential solvation in the chloroform-HBA binary mixtures and the preference of one solvent above the other in the solvation shell have been attributed to the hydrogen bond donor and acceptor ability of the solvent mixtures. HBA solvents form a strong hydrogen bond with the amino group while chloroform forms a hydrogen bond with the nitro group of PNA. This specific functional group recognition increases the local concentration at specific sites resulting in location specific preferential solvation and synergistic preferential solvation. Solvents with comparable polarity have been found to show significant synergistic behavior as a result of the formation of stronger solvent-solvent hydrogen bonded S1-S2 species. These propositions were found to be supported by theoretical solvation models, calculated HOMO-LUMO energy gaps, the effect of deuterated solvent on the extent of PS, and 1H NMR spectral analyses.

Solvent Effects on Protonation Constants of Imatinib in Different Aqueous Solutions of Methanol at T = 298.15 K

Imatinib (Gleevec) is a drug that is applied to treat cancer. It inhibits the Bcr-Abl tyrosine-kinase and therefore, it can slow growth or result in programmed cell death of certain types of cancer cells. In 2001, the United States approved this drug. The protonation constants of imatinib were determined in mixed solvent of water and methanol containing 40, 50, 60, 70, and 80% (v/v) of methanol, using a combination of spectrophotometric and potentiometric methods at T = 298.15 K and constant ionic strength (0.1 mol dm–3 NaClO4). The obtained protonation constants were analyzed using Kamlet, Abboud, and Taft parameters. In this study, a good linear relationship was obtained between protonation constants (on the logarithmic scale) and dielectric constant (ɛ) of the water-methanol solvent. Dual-parameter correlation of log K versus π* (dipolarity/polarizability) and α (hydrogen-bond donor acidity), as well as versus π* and β (hydrogen-bond acceptor basicity) and multi-parameter π*, α, and β, gave good results for various mole fraction of methanol in methanol-water solvent. Finally, the results are discussed in terms of the solvent effect (increasing of mole fraction of methanol in methanol-water solvent) on the protonation constants.

Solute–Solvent and Solvent–Solvent Interactions and Preferential Solvation of 1,1-Diamino-2,2-dinitroethylene in Aqueous Co-solvent Mixtures of N,N-Dimethylformamide and Dimethyl Sulfoxide

The effects of solvent properties on 1,1-diamino-2,2-dinitroethylene (FOX-7) solubility were investigated from the solubility values in aqueous co-solvent mixtures of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in terms of the linear solvation energy relationships with use of mathCAD software. For both aqueous mixtures, the main effect of hydrogen bond basicity was observed based on the solubility variation of FOX-7. The preferential solvation (the difference in composition between the solvation shell of the solute and the bulk composition in a mixture) of FOX-7 in the two aqueous of co-solvent solutions were investigated by using the method of inverse Kirkwood–Buff integrals (IKBI). The values of the preferential solvation parameters (δx1,3) were negative in water-rich mixtures, which are − 3.103×10−2 to − 2.936 × 10−2 for DMF (1) + water (2) mixtures and − 4.470 × 10−2 to − 3.995 × 10−2 for DMSO (1) + water (2) mixtures. However, in the co-solvent compositions ranging from 0.19 or 0.21 to 1 in mole fraction of DMF or DMSO, positive values of δx1,3 were observed. The preference of FOX-7 in water-rich mixtures can be explained based on the higher acidic behavior of FOX-7 molecules, which interact with the proton–acceptor functional groups of DMF and DMSO. KAT-LSER analysis showed that only the hydrogen-bond acceptor basicity of solvents played an important role on the FOX-7 solubility owing to its two amino functional groups. The squared correlation coefficient and F-statistic values are 0.98 and 314 for DMF + water mixture, and 0.96 and 130 for DMSO + water mixture, respectively.

Solvent property-ion conductivity relationship for lithium, sodium and potassium ions in non-aqueous solvents using QSER

Non-aqueous solvents are applicable in industrial and chemical reactions as well as some analytical methods such as electrochemistry. Application of quantitative structure-electrochemistry relationship (QSER) modeling in non-aqueous media can reduce trial-and-error experiments and more accurate estimation of target properties with lower number of runs. In the current study, for the first time, QSER was applied in conductometry as a wide field in electrochemistry. The target properties for modeling were the limiting molar conductivities of three alkali metal ions (Li+, Na+, K+) in water and various organic solvents; and empirical scales of the utilized solvents were applied as the independent set of variables. R2 in training sets of Li+, Na+ and K+ models were 0.94, 0.95 and 0.90 respectively. Models also showed good prediction ability and R2 in test sets of Li+, Na+ and K+ models were 0.95, 0.94 and 0.98 respectively. In addition, more statistical evaluations were done to show the predictability and stability of proposed QSERs. One of the advantages of suggested QSER models based on solvent empirical scales is the clear meaning of the solvent scales and their ability in description of solute-solvent interactions. Based on obtained results, the impact of some solvent features such as electron-donating power, electron-donating power, dipolarity-dipolarizability, hydrogen bonding, hydrogen-bond acceptor basicity and solvent acceptor number on the conductivity of lithium, sodium and potassium ions were discussed.

Effect of an Intrinsically Disordered Plant Stress Protein on the Properties of Water

Dehydrins are plant proteins that are able to protect plants from various forms of dehydrative stress such as drought, cold, and high salinity. Dehydrins can prevent enzymes from losing activity after freeze/thaw treatments. Previous studies had suggested that the dehydrins function by a molecular shield effect, essentially preventing a denatured enzyme from aggregating with another enzyme. Therefore, the larger the dehydrin, the larger the shield and theoretically the more effective the protection. Although this relationship holds for smaller dehydrins, it fails to explain why larger dehydrins are less efficient than would be predicted from their size. Using solvatochromic dyes to probe the solvent features of water, we first confirm that the dehydrins do not bind the dyes, which would interfere with interpretation of the data. We then show that the dehydrins have an effect on three solvent properties of water (dipolarity/polarizability, hydrogen-bond donor acidity and hydrogen-bond acceptor basicity), which can contribute to the protective mechanism of these proteins. Interpretation of these data suggests that although polyethylene glycol and dehydrins have similar protective effects, dehydrins may more efficiently modify the hydrogen-bonding ability of bulk water to prevent enzyme denaturation. This possibly explains why dehydrins recover slightly more enzyme activity than polyethylene glycol.

Kinetic analysis of tautomer forms of aromatic-urea compounds with acetate ions: solvent effect of excited state intermolecular proton transfer.

In this paper, we report the solvent effect of excited state intermolecular proton transfer (ESIPT) reactions of urea compounds in the presence of tetrabutylammonium acetate (TBAAc). We prepared anthracene-urea compounds (9An and 2An), a pyrene-urea compound (Py) and an anthracene-diurea compound (9,10An), which have alkylsulfonyl groups to improve their solubility in various organic solvents. We investigated the solvent effects of the ESIPT reaction using absorption, fluorescence, and 1H NMR spectroscopy along with fluorescence decay measurements in dimethyl sulfoxide (DMSO), acetonitrile (MeCN), tetrahydrofuran (THF) and toluene. The tautomer fluorescence of 9An showed remarkable solvent dependence on the spectral red-shift compared with 2An, Py and 9,10An. As a result of the detailed spectroscopic investigations with regard to the solvent including kinetic analysis of the ESIPT for 9AnAcO-, we revealed that the energy gap between the normal and tautomer forms in the excited state depended on the hydrogen bond acceptor basicity (β), which is one of the Kamlet-Taft solvent parameters. Finally, we discovered that the tautomer structures of aromatic-urea compounds were stabilized by hydrogen bond interactions.

Phase equilibria, solvent properties, and protein partitioning in aqueous polyethylene glycol-600-trimethylamine N-oxide and polyethylene glycol-600-choline chloride two-phase systems

The phase diagram of a new aqueous two-phase system (ATPS) formed by polyethylene glycol with molecular weight 600 (PEG-600) and trimethylamine N-oxide (TMAO) in 0.01 M sodium phosphate buffer (NaPB), pH 7.4, is determined and hydrophobic, electrostatic and other solvent properties of the phases are characterized. The same properties are determined for the ATPS formed by PEG-600 and choline chloride in 0.01 M sodium phosphate buffer (NaPB), pH 7.4. Solvent properties of water (dipolarity/polarizability, hydrogen bond donor acidity, and hydrogen bond acceptor basicity) in aqueous solutions of polypropylene glycol-400 (PPG-400), polyethylene glycol dimethyl ether -250 (PEGDME-250), and choline chloride are determined at different concentrations. The concentrations of the aforementioned polymers, as well as PEG-600 and PEG-1000 required for phase separation in mixtures with choline chloride reported in the literature are analyzed. It is found that the concentrations of polymers needed for phase separation in mixtures with 35%wt. choline chloride are linearly related with water hydrogen bond donor acidity or hydrogen bond acceptor basicity in the individual polymer solutions at given concentrations. Partition behavior of nine proteins was examined in both systems. The partition coefficients of proteins in PEG-600-choline chloride ATPS exceeded those observed in PEG-600-TMAO ATPS from ca. 2 to ca. 75-fold possibly due to the larger difference between the composition of the coexisting phases in the former ATPS. Analysis of partition coefficients in the two ATPS were compared to those reported in Dextran-PEG ATPS, and proteins likely engaged in direct interactions with choline chloride were identified.

Intermolecular interactions upon carbon dioxide capture in deep-eutectic solvents.

Herein we report the CO2 uptake in potential deep-eutectic solvents (DESs) formed between hydrogen bond acceptors (HBAs) such as monoethanolammonium chloride ([MEA·Cl]), 1-methylimidazolium chloride ([HMIM·Cl]) and tetra-n-butylammonium bromide ([TBAB]) and hydrogen bond donors (HBDs) like ethylenediamine ([EDA]), diethylenetriamine ([DETA]), tetraethylenepentamine ([TEPA]), pentaethylenehexamine ([PEHA]), 3-amino-1-propanol ([AP]) and aminomethoxypropanol ([AMP]) and analyzed the outcome in terms of the specific polarity parameters. Among various combinations of HBAs and HBDs, [MEA·Cl][EDA]-, [MEA·Cl][AP]-, [HMIM·Cl][EDA]- and [HMIM·Cl][AP] showed excellent CO2 uptake which was further improved upon increasing the mole ratio of HBA : HBD from 1 : 1 to 1 : 4. The lowest CO2 uptake in [MEA·Cl][PEHA] (12.7 wt%) and [HMIM·Cl][PEHA] (8.4 wt%) despite the highest basicity of [PEHA] infers that the basicity is not the sole criteria for guiding the CO2 uptake but, in reality, CO2 capture in a DES relies on the interplay of H-bonding interactions between each HBA and HBD. The role of HBAs in guiding CO2 uptake was more prominent with weak HBDs such as [TEPA] and [PEHA]. The speciation of absorbed CO2 into carbamate, carbonate, and bicarbonate was favorable in DES characterized by comparable hydrogen bond donor acidity (α) and hydrogen bond acceptor basicity (β) values, whereas the conversion of carbamate to carbonate/bicarbonate was observed to depend on α. The addition of water in DES resulted in lower CO2 uptake due to the decreased basicity (β).

Investigation of alternative supported liquid membranes in electromembrane extraction of basic drugs from human plasma

For the first time, supported liquid membranes (SLMs) of phthalate- and nitrile-based organic solvents were investigated for electromembrane extraction (EME) of eleven polar and non-polar basic drugs from human plasma (pH 7.4). Several phthalates and nitriles which possess high hydrogen bond acceptor basicity, zero hydrogen bond donor acidity, and certain level of hydrophobicity (3 < log P < 5.5) were identified as new and efficient SLMs. The new solvents provided low extraction current, and contained no solvent impurities contaminating the acceptor solution when analyzed by HPLC-UV. Extraction recoveries, kinetics, and even selectivity with diallyl phthalate and dodecanenitrile were similar to 2-nitrophenyl octyl ether (NPOE), although they comprised totally different functional groups. Water penetration into the SLM during EME was investigated for the first time and analyzed by Fourier transform infrared spectrometry. Interestingly, no water was observed penetrating into solvents which are only efficient for EME of nonpolar basic drugs, while water was found to penetrate into the SLM solvents which are efficient for EME of polar basic drugs.