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Projeto de investigação
Desenvolvimento de uma tecnologia sustentável para a extração e purificação de clorofilas a partir de biomassa
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Interactions of pyridinium, pyrrolidinium or piperidinium based ionic liquids with water: measurements and COSMO-RS modelling
Publication . Khan, Imran; Taha, Mohamed; Pinho, Simão; Coutinho, João A.P.
Looking for a better knowledge concerning water and ionic liquids (ILs) interactions, a systematic study
of the activity coefficients of water in pyridinium, pyrrolidinium and piperidinium-based ILs at 298.2 K is
here presented based on water activity measurements. Additionally, the study of the structural effects of
the pyridinium-based cation is also pursued. The results show that non-aromatic ILs are interacting more
with water than aromatic ones, and among the ortho, meta and para isomers of 1-butyl-methylpyridinium
chloride, the ortho position confers a more hydrophilic character to that specific IL. The physicalchemistry
of the solutions was interpreted based on dissociation constants, natural bond orbitals and
excess enthalpies providing a sound basis for the interpretation of the experimental observations. These
results show that hydrogen bonding controls the behavior of these systems, being the anion-water one of
the most relevant interactions, but modulated by the anionecation interactions.
Why are some cyano-based ionic liquids better glucose solvents than water?
Publication . Batista, Marta; Passos, Helena; Henriques, Bruno J.M.; Maginn, Edward J.; Pinho, Simão; Freire, Mara G.; Gomes, J.R.B.; Coutinho, João A.P.
Among different classes of ionic liquids (ILs), those with cyano-based anions have been of special interest due
to their low viscosity and enhanced solvation ability for a large variety of compounds. Experimental results
from this work reveal that the solubility of glucose in some of these ionic liquids may be higher than in water –
a well-known solvent with enhanced capacity to dissolve mono- and disaccharides. This raises questions on
the ability of cyano groups to establish strong hydrogen bonds with carbohydrates and on the optimal
number of cyano groups at the IL anion that maximizes the solubility of glucose. In addition to experimental
solubility data, these questions are addressed in this study using a combination of density functional theory
(DFT) and molecular dynamics (MD) simulations. Through the calculation of the number of hydrogen bonds,
coordination numbers, energies of interaction and radial and spatial distribution functions, it was possible to
explain the experimental results and to show that the ability to favorably interact with glucose is driven by
the polarity of each IL anion, with the optimal anion being dicyanamide.
Effect of the cation on the interactions between alkyl methyl imidazolium chloride ionic liquids and water
Publication . Khan, Imran; Taha, Mohamed; Ribeiro-Claro, Paulo J.A.; Pinho, Simão; Coutinho, João A.P.
A systematic study of the interactions between water and alkyl methyl imidazolium chloride ionic liquids at 298.2 K, based on activity coefficients estimated from water activity measurements in the entire solubility range, is presented. The results show that the activity coefficients of water in the studied ILs are controlled by the hydrophilicity of the cation and the cation-anion interaction. To achieve a deeper understanding on the interactions between water and the ILs, COSMO-RS and FTIR spectroscopy were also applied. COSMO-RS was used to predict the activity coefficient of water in the studied ionic liquids along with the excess enthalpies, suggesting the formation of complexes between three molecules of water and one IL molecule. On the basis of quantum-chemical calculations, it is found that cation-anion interaction plays an important role upon the ability of the IL anion to interact with water. The changes in the peak positions/band areas of OH vibrational modes of water as a function of IL concentration were investigated, and the impact of the cation on the hydrogen-bonding network of water is identified and discussed.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
5876-PPCDTI
Número da atribuição
EXPL/QEQ-PRS/0224/2013