Browsing by Author "Abranches, Dinis O."
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- Can cholinium chloride form eutectic solvents with organic chloride-based salts?Publication . Abranches, Dinis O.; Silva, Liliana P.; Martins, Mónia A.R.; Fernandez, Luis; Pinho, Simão; Coutinho, João A.P.The high melting point of a large number of organic salts with potential ionic liquid-like properties, hinders their applicability as solvents. Considering the success of cholinium chloride on lowering the melting temperature of several substances and its success on forming deep eutectic solvents, this work studies its mixing with organic chlorides to lower their melting points producing eutectic ionic liquids. The solid-liquid phase diagrams for binary mixtures composed of cholinium chloride and ten organic halides were experimentally measured. Surprisingly, cholinium chloride presented, for all these systems, significant positive deviations from ideal liquid behaviour that restricted its ability to lower the melting points of these mixtures. Only for mixtures with ammonium chloride, tetramethylammonium chloride, bis(2-hydroxyethyl)dimethylammonium chloride or cholinium bromide was cholinium chloride able to significantly lower the melting point of the mixture, but without reaching values close to room temperature (298 K). For a better understanding of the results obtained, the solid-liquid phase diagrams of four alkylammonium chloride-based mixtures were experimentally assessed and used to show that these compounds are better than cholinium chloride at inducing negative deviations from ideality, leading to greater melting point depressions.
- Designing type V deep eutectic solvents with antimalarial pharmaceutical ingredientsPublication . Teixeira, Gabriel; Brandão, Paula; Ferreira, Ana I.M.C. Lobo; Abranches, Dinis O.; Santos, L.uís M.N.B.F.; Ferreira, Olga; Coutinho, João A.P.This work studies the formation of deep eutectic solvents formed by one active pharmaceutical ingredient (quinine, pyrimethamine, or 2-phenylimidazopyridine) and a second component potentially acting as an excipient (betaine, choline chloride, tetramethylammonium chloride, thymol, menthol, gallic acid, vanillin, acetovanillone, 4-hydroxybenzaldehyde, syringaldehyde, propyl gallate, propylparaben, or butylated hydroxyanisole), aiming to address challenges regarding drug solubility, bioavailability, and permeability. A preliminary screening was carried out using the thermodynamic model COSMO-RS, narrowing down the search to three promising excipients (thymol, propyl gallate, and butylated hydroxyanisole). Nine solid–liquid equilibrium (SLE) phase diagrams were experimentally measured combining the three model drugs with the screened excipients, and using a combination of a visual melting method and differential scanning calorimetry. Negative deviations from thermodynamic ideality were observed in all nine systems. Furthermore, a total of four new cocrystals were found, with powder and single crystal X-ray diffraction techniques being employed to verify their unique diffraction patterns. In the thermodynamic modelling of the SLE diagrams, two COSMO-RS parametrizations (TZVP and TZVPD-FINE) were also applied, though neither consistently delivered a better description over the other.
- Enhancing artemisinin solubility in aqueous solutions: searching for hydrotropes based on ionic liquidsPublication . Sales, Isabela; Abranches, Dinis O.; Costa, Pedro; Sintra, Tânia E.; Ventura, Sónia P.M.; Mattedi, Silvana; Coutinho, João A.P.; Freire, Mara G.; Pinho, SimãoArtemisinin is a sesquiterpenoid lactone peroxide, known for its potent antimalarial activity that can be extracted from Artemisia annua L. This compound is only sparingly soluble in water, making its extraction using environmental-friendly and non-toxic aqueous solvents difficult. In the attempt to overcome this limitation, hydrotropes, which are a class of compounds that can assist in increasing the solubility of hydrophobic solutes in water, were investigated in this work. In particular, the hydrotropic capability of ionic liquids (ILs) on the aqueous solubility of artemisinin was studied. The effects of IL concentration and anion nature of 1-butyl-3-methylimidazolium-based ILs on the solubility of artemisinin at 303.2 K in water were evaluated. It is here shown the excellent capacity of ILs containing thiocyanate or dicyanamide anions to enhance the solubility of artemisinin in aqueous media, with a magnitude comparable to that obtained with the best organic solvents. Furthermore, solvatochromic parameters of the ILs aqueous solutions were also measured and combined with COSMO-RS and the cooperative hydrotropy model to establish relations between the artemisinin solubility enhancement and the solvent characteristics. The solubility enhancement of artemisinin is favored by the apolarity of the medium and the lower hydrogen-bond acceptor character of the hydrotrope.
- Estimating the melting temperatures of type V deep eutectic solventsPublication . Teixeira, Gabriel; Abranches, Dinis O.; Ferreira, Olga; Coutinho, João A.P.The recently proposed category of type V deep eutectic solvents (DESs), composed only of non-ionic species, has attracted great interest in the literature. However, despite their importance in solvent design, measuring the solid−liquid equilibrium (SLE) diagrams of all possible type V DES precursor combinations is unfeasible. Therefore, a reliable computational tool must be found to estimate SLE phase diagrams and, thus, the melting points of type V DESs. In this work, a total of 134 different binary eutectic systems (1744 datapoints) were gathered from the literature, and the calculation capabilities and accuracy of three different models COSMO-RS, UNIFAC of Dortmund, and Group and Group-Interaction Contribution method (GGIC) were evaluated. UNIFAC and COSMO-RS were, by far, the best performing models, with average absolute deviations (AADs) of, respectively, 6.9 K for 94 systems and 7.4 K for 133 systems. Due to a lack of group interaction parameters, UNIFAC could only describe 94 systems, a severe disadvantage over COSMO-RS. Moreover, despite being able to describe all 134 systems, the GGIC model resulted in an AAD of 37 K. Finally, the effect of using the different parametrizations or multiple conformers in COSMO-RS predictions was also evaluated, and the validity of neglecting heat capacity terms when performing SLE calculations was verified.
- Experimental solubility and density studies on aqueous solutions of quaternary ammonium halides, and thermodynamic modelling for melting enthalpy estimationsPublication . Vilas-Boas, Sérgio M.; Abranches, Dinis O.; Crespo, Emanuel A.; Ferreira, Olga; Coutinho, João A.P.; Pinho, Simão
- Exploring the role of temperature on hydrotropyPublication . Abranches, Dinis O.; Soares, Bruna P.; Cordova, Isabella Weber; Benfica, Jordana; Ferreira, Olga; Pinho, Simão; Coutinho, João A.P.Aqueous solubility can be enhanced through hydrotropy, where an amphiphilic molecule (the hydrotrope) ag-gregates around the solute, boosting its solubility. To understand the impact of temperature on this phenomenon, the solubility of syringic acid was measured in aqueous solutions of different bio-based hydrotropes. Solubility curves were modelled using Gaussian processes, a powerful class of machine learning interpolators. This allowed for a thermodynamic analysis of excess solvation properties that was complemented using the COSMO-RS model. As expected, the absolute solubility of syringic acid increased with temperature. However, at low hydrotrope concentrations, this increase was not driven by interactions in the liquid phase. Thus, the solubility enhancement of syringic acid was found to be independent of temperature. Conversely, at high hydrotrope concentrations, increasing the temperature significantly decreased the solubility enhancement of the solute. These effects were interpreted considering different solubilization mechanisms, namely hydrotropy (low hydrotrope concentrations) and co-solvency (high hydrotrope concentrations).
- Extensive characterization of choline chloride and its solid–liquid equilibrium with waterPublication . Ferreira, Ana I.M.C. Lobo; Vilas-Boas, Sérgio M.; Silva, Rodrigo M.A.; Martins, Mónia A.R.; Abranches, Dinis O.; Paz, Filipe A. Almeida; Ferreira, Olga; Pinho, Simão; Santos, Luís M.N.B.F.; Coutinho, João A.P.The importance of choline chloride (ChCl) is recognized due to its widespread use in the formulation of deep eutectic solvents. The controlled addition of water in deep eutectic solvents has been proposed to overcome some of the major drawbacks of these solvents, namely their high hygroscopicities and viscosities. Recently, aqueous solutions of ChCl at specific mole ratios have been presented as a novel, low viscous deep eutectic solvent. Nevertheless, these proposals are suggested without any information about the solid–liquid phase diagram of this system or the deviations from the thermodynamic ideality of its precursors. This work contributes significantly to this matter as the phase behavior of pure ChCl and (ChCl + H2 O) binary mixtures was investigated by calorimetric and analytical techniques. The thermal behavior and stability of ChCl were studied by polarized light optical microscopy and differential scanning calorimetry, confirming the existence of a solid–solid transition at 352.2 0.6 K. Additionally, heat capacity measurements of pure ChCl (covering both ChCl solid phases) and aqueous solutions of ChCl (xChCl o 0.4) were performed using a heat-flow differential scanning microcalorimeter or a high- precision heat capacity drop calorimeter, allowing the estimation of a heat capacity change of (ChCl) E 39.3 10 J K 1 mol 1 , between the hypothetical liquid and the observed crystalline phase at 298.15 K. The solid–liquid phase diagram of the ChCl + water mixture was investigated in the whole concentration range by differential scanning calorimetry and the analytical shake-flask method. The phase diagram obtained for the mixture shows an eutectic temperature of 204 K, at a mole fraction of choline chloride close to xChCl = 0.2, and a shift of the solid–solid transition of ChCl–water mixtures of 10 K below the value observed for pure choline chloride, suggesting the appearance of a new crystalline structure of ChCl in the presence of water, as confirmed by X-ray diffraction. The liquid phase presents significant negative deviations to ideality for water while COSMO-RS predicts a near ideal behaviour for ChCl.
- Glycerol ethers as hydrotropes and their use to enhance the solubility of phenolic acids in waterPublication . Soares, Bruna de Paula; Abranches, Dinis O.; Sintra, Tânia E.; Leal-Duaso, Alejandro; García, José Ignacio; Pires, Elísabet; Shimizu, Seishi; Pinho, Simão; Coutinho, João A.P.The use of glycerol ethers (with alkyl side chain ranging from one to six methyl groups) as hydrotropes to enhance the solubility of gallic and syringic acids in water was here studied. These compounds were selected due to their biological and industrial applications and for serving as model molecules for lignin solubilization. The results obtained were compared against traditional co-solvents, demonstrating the exceptional hydrotropic ability of glycerol ethers. Setschenow constants show that the hydrophobicities of both solute and hydrotrope play an important role in the solubility enhancement by hydrotropy, shedding light into its molecular mechanism. The solubility curves of gallic acid and syringic acid in the aqueous glycerol ether solutions were fitted using a recently proposed statistical thermodynamics-based model. This allowed the estimation of solute recovery from hydrotropic solution by using water as antisolvent. Unlike what is usually claimed it is here shown that in some conditions it is impossible to recover the solute by simply adding water. This analysis paves the way for a rational design and selection of hydrotropes, in which both solubility enhancement and solute recovery are critical parameters to be taken into account.
- Greener terpene-terpene eutectic mixtures as hydrophobic solventsPublication . Martins, Mónia A.R.; Silva, Liliana P.; Schaeffer, Nicolas; Abranches, Dinis O.; Maximo, Guilherme J.; Pinho, Simão; Coutinho, João A.P.Natural products can be the basis for the development of green solvents, relevant for the advancement of new, more sustainable processes and products. In this work, 10 binary mixtures constituted by terpenes are prepared and characterized. Their solid−liquid phase diagrams show that room-temperature solvents can be prepared from solid terpenes in a wide composition range. These diagrams are accurately described by the conductor-like screening model for real solvents, showing it to be a useful predictive tool for the design of novel natural solvents. At the eutectic point, these mixtures possess low viscosities, densities lower than water, and high boiling temperatures. The low water solubility in the eutectic solvents together with its negligible impact on the properties measured is a strong indicator of the hydrophobic character of these mixtures. The tunable character of these mixtures is demonstrated by studying the solvatochromic parameters in the entire concentration region, the properties of the final solvents being tuned by simply varying the mole fraction of the terpenes. The high potential of this tunable character is shown in the selective extraction of dyes from their aqueous solutions. This work is expected to devise new insights concerning these solvents as well as to boost their application in green industrial processes.
- Insights into the chloride versus bromide effecton the formation of urea quaternary ammonium eutectic solventsPublication . Martins, Mónia A.R.; Abranches, Dinis O.; Silva, Liliana P.; Pinho, Simão; Coutinho, João A.P.The intermolecular interactions of urea and quaternary ammonium salts relevant to their thermodynamic nonideality were here investigated by measuring the solid-liquid equilibria of their binary mixtures. The experimental data revealed that the anion transfer between the quaternary ammonium salt and urea increases with increasing alkyl chain lengths, leading to negative deviations from ideality in the urea-rich side for [N4,4,4,4]- based systems. However, the use of bromides instead of chlorides dampens the nonideality of urea because of larger size and lower electronegativity of the anion. The behavior of urea when mixed with ChCl or ChBr was found to be remarkably different, indicating that its nonideality in the ChCl/urea eutectic solvent is governed by urea-chloride rather than hydroxyethyl-urea interactions. The conclusions presented highlight the contribution of charge delocalization in the formation of deep eutectic solvents of type III.
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