Tuning the physicochemical properties of protic-aprotic ionic liquids upon reciprocal binary mixing

The alterations in properties of protic/aprotic (2-hydroxyethylammonium formate)/ 1-butyl-3-methylimidazolium methyl sulfate) ionic liquids (ILs), based on reciprocal binary mixing concept ([A][B][X][Y]) have been investigated by studying the density, speed of sound, and viscosity of mixtures as a function of temperature. The volume of mixing, isentropic compressibility, excess molar isentropic compressibilities and activation energy of viscous flow have been derived, which indicate a very high level of non-ideality in the mixtures desired to take advantage of improved solvent properties. FTIR spectral analysis and solvatochromic parameters (normalized Reichardt’s parameter, dipolarity/polarizibility, hydrogen bond donor and acceptor coefficients) determined through the solvatochromic probes have been utilized to examine the hydrogen bonding and ion-ion interactions prevailing in the studied systems. Although significant alterations in hydrogen bonding and ion-ion interactions are observed, dispersion type interactions dominate over chemical interactions as indicated by a high positive deviations in the volumes of mixing

Solvatochromism in Solvent Mixtures: A Practical Solution for a Complex Problem

Many reactions are carried out in solvent mixtures, mainly because of practical reasons. For example, E2 eliminations are favored over SN2 substitutions in aqueous organic solvents because the bases are desolvated. This example raises the question: how do we chose binary solvents to favor reaction outcomes? This important question is deceptively simple because it requires that we understand the details of all interactions within the system. Solvatochromism (solvent-dependent color change of a substance) has contributed a great deal to answer this difficult question, because it gives information on the interactions between solvents, solute-solvent, and presumably transition state-solvent. This wealth of information is achieved by simple spectroscopic measurements of selected (solvatochromic) substances, or probes. An important outcome of solvatochromism is that the probe solvation layer composition is almost always different from that of bulk mixed solvent. In principle, this difference can be exploited to “tune” the composition of solvent mixture to favor the reaction outcome. This minireview addresses the use of solvatochromic probes to quantify solute-solvent interactions, leading to a better understanding of the complex effects of solvent mixtures on chemical phenomena. Because of their extensive use in chemistry, we focus on binary mixtures containing protic-, and protic-dipolar aprotic solvents

Estimation of speed of sound in binary mixtures of cyclohexane with benzene, benzaldehyde or cyclohexylamine, and, cyclohexylamine with benzene in the temperature range (293.15–323.15) K employing empirical and theoretical models

492-497Speed of sound in the binary mixtures of cyclohexane with benzene, benzaldehyde or cyclohexylamine, and, that of cyclohexylamine with benzene over the entire composition range and at (293.15, 303.15, 313.15 and 323.15) K has been estimated employing several models, viz., Nomoto model (NM), Van Dael model (VM), Junjie model (JM), Ernst et al. model (EM), Impedance model (IM), Collision factor theory (CFT), Intermolecular free length theory (FLT), and, Prigogine-Flory-Patterson theory (PFPT). <span style="font-size:9.0pt; mso-bidi-font-size:11.0pt" lang="EN-US">The maximum deviations between estimated and experimental speed of sound by different models NM, VDM, JM, EM, IM, CFT, FLT, and PFPT are –24.5, –23.0, 20.2, –48.3, –22.1, –24.9, 25.0, and 24.4 m s-1, respectively. The values of standard percentage deviations for NM, VDM, JM, EM, IM, CFT, FLT, and PFPT models are in the range of 0.3–1.4, 0.3–1.4, 0.3–1.1, 0.3–2.7, 0.5–1.2, 0.2–1.4, 0.4–1.2, and 0.4–1.2%, respectively. Considering the overall results, the FLT model predicts the most accurate values for speed of sound while the EM model gives the least accurate values. </span

Tuning the physicochemical properties of protic-aprotic ionic liquids upon reciprocal binary mixing

544-553<span style="font-size:9.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" "times="" roman";mso-ansi-language:en-gb;mso-fareast-language:en-us;="" mso-bidi-language:hi"="" lang="EN-GB">The alterations in properties of protic/aprotic (2-hydroxyethylammonium formate)/ 1-butyl-3-methylimidazolium methyl sulfate) ionic liquids (ILs), based on reciprocal binary mixing concept ([A][B][X][Y]) have been investigated by studying the density, speed of sound, and viscosity of mixtures as a function of temperature. The volume of mixing, isentropic compressibility, excess molar isentropic compressibilities and activation energy of viscous flow have been derived, which indicate a very high level of non-ideality in the mixtures desired to take advantage of improved solvent properties. FTIR spectral analysis and solvatochromic parameters (normalized Reichardt’s parameter, dipolarity/polarizibility, hydrogen bond donor and acceptor coefficients) determined through the solvatochromic probes have been utilized to examine the hydrogen bonding and ion-ion interactions prevailing in the studied systems. Although significant alterations in hydrogen bonding and ion-ion interactions are observed, dispersion type interactions dominate over chemical interactions as indicated by a high positive deviations in the volumes of mixing.</span

Influence of imidazolium ionic liquids on fluorescence of push-pull diphenylbutadienes

A series of donor–acceptor substituted diphenylbutadienes have been synthesized and their fluorescence properties in organic solvents and imidazolium ionic liquid media were investigated. Substituted diphenylbutadienes show remarkable solvatochromic emission in polar solvents and in ionic liquids due to intramolecular charge transfer. Interestingly, diphenylbutadiene containing methoxy donor and nitro acceptor exhibits excitation dependent emission behaviour in ethanol. Excitation dependent emission studies of fluorophores in ionic liquids show distinct emission signals due to the locally excited and the charge transfer states revealing the existence of two species. Time resolved experiments show single exponential decay in organic solvents and bi-exponential decay in ionic liquids media,an indication of interaction of fluorophores with different microenvironments.by Anuji K. Vasu et al

Nonideal Behavior of Aqueous Deep Eutectic Solvents Based on Tetrabutylphosphonium Bromide and Ethylene Glycol/Glycerol

Understanding the effect of solvents on the thermophysical properties of deep eutectic solvents (DESs) is crucial to utilize their green credentials in several industrial processes. Herein, we explore the nonideal behavior of aqueous DES mixtures to better understand the prevailing intermolecular interactions within them. The used DESs are composed of tetrabutylphosphonium bromide and ethylene glycol/glycerol. The nonideal behavior is explored through calculating the excess molar volume (VmE) and viscosity deviation (ln ηm) over the entire range of compositions and the temperature range from 293.15 to 323.15 K at 101.3 kPa pressure. The values of VmE and ln ηm are fitted with the Redlich–Kister-type polynomial equation. The negative VmE and ln ηm values indicate the strong H-bonding interactions between the DES and water and destruction of the DES structure. The experimentally calculated values of VmE are further evaluated using the well-known Prigogine–Flory–Patterson (PFP) theory and extended real association (ERAS) model. Looking at their increasing utilization, we believe that the results of the present study will be beneficial for designing various industrial equipment and processes

Thermo-Switchable de Novo Ionic Liquid-Based Gelators with Dye-Absorbing and Drug-Encapsulating Characteristics

An ionic liquid-based surfactant with ester functionality self-aggregates in an aqueous medium and forms ionogels at 8.80% (w/v) concentration at physiological pH. The ionogel exhibited a remarkable change in its appearance with temperature from fibrillar opaque to transparent because of the dynamic changes within its supramolecular structure. This gel-to-gel phase transition occurs below the melting point of the solid ionic liquid. The ionogels were investigated using turbidity, differential scanning calorimetry, scanning electron microscopy (SEM), field emission SEM (FE-SEM), inverted microscopy, transmission electron microscopy imaging, Fourier transform infrared spectroscopy, and rheological measurements. The fibrillar opaque ionogel and transparent ionogel were studied for their ability to absorb dyes (methyl orange and crystal violet) and to encapsulate drugs (diclofenac sodium and imatinib mesylate)

Bio-ionic liquid based self healable and adhesive ionic hydrogel for the on-demand transdermal delivery of chemotherapeutic drug

The non-invasive nature and potential for sustained release makes transdermal drug administration an appealing treatment option for cancer therapy. However, the strong barrier of the stratum corneum (SC) poses a challenge for the penetration of hydrophilic chemotherapy drugs such as 5-Fluorouracil (5-FU). Due to their biocompatibility and capacity to increase drug solubility and permeability especially when paired with chemical enhancers, as in oleic acid (OA) used in this work, choline glycinate ([Cho][Gly]), has emerged as a potential class of substances for transdermal drug delivery. In this work, we examined the possibility of transdermal delivery of 5-FU for the treatment of breast cancer using an ionic hydrogel formulation consisting of [Cho][Gly] with OA. Small angle neutron scattering, rheological analysis, field emission scanning electron microscopy, and dynamic light scattering analysis were used to characterize the ionic hydrogel. Non-covalent interactions present between [Cho][Gly] and OA were investigated by computational simulations and FTIR spectroscopic methods. When subjected to the in vitro drug permeation using goat skin in Franz diffusion cell, the hydrogel demonstrated sustained release of 5-FU and effective permeability in the order: [Cho][Gly]-OA gel > [Cho][Gly] > PBS (control). The hydrogel also demonstrated 92% cell viability after 48 hours for the human keratinocyte cell line HaCaT cells as well as the normal human cell line L-132. Breast cancer cell lines MCF-7 and cervical cancer cell line HeLa were used to study in vitro cytotoxicity that was considerably affected by the 5-FU-loaded hydrogel. These results indicate the potential of the hydrogel as a transdermal drug delivery vehicle for the treatment of breast cancer

Molecular interaction study through experimental and theoretical volumetric, transport and refractive properties of <i>N</i>-ethylaniline with aryl and alkyl ethers at several temperatures

<div><p>ABSTRACT</p><p>To investigate the molecular interaction study between secondary amine with aryl and alkyl ether, we report densities, speeds of sound, viscosities and refractive indices of <i>N</i>-ethylaniline (NEA) with aryl (anisole, phenetole) and alkyl (tert-butyl methyl ether) ether over the entire composition regime and in the temperature range of 293.15–323.15 K at 5 K intervals. Various excess and transport properties were derived from the experimental data and the excess parameters were fitted to the Redlich–Kister polynomial equation using multiparametric non-linear regression analysis to derive the binary coefficients and to estimate the standard deviation. Molecular interactions between the unlike molecules were analysed through dipole–dipole interactions, cross-association between the components of the mixtures and H-bond formation. Viscosity and refractive index of the mixtures were predicted through several empirical equations and compared with the experimental results. Prigogine–Flory–Patterson statistical theory was used to predict the excess molar volume results.</p></div