Understanding ion-ion and ion-solvent interactions in aqueous solutions of NMP based protic ionic liquids through partial molar properties and DFT calculations
Graphical abstract
Ion-ion and ion-solvent interactions in aqueous solutions of NMP based protic ionic liquids.
Introduction
Ionic liquids (ILs) have received increasing attention for their potential scientific and industrial applications [1], [2], [3]. Because of their unique physicochemical properties such as wide electrochemical window, negligible vapor pressures, high thermal stability, broad liquid temperature ranges, and specific solvent abilities, ILs are being employed as ‘designer solvent’ for targeted application [2], [4], [5], [6].
ILs can be classified as protic ionic liquid (PIL) and aprotic ionic liquid (AIL), the former involves the proton transfer between a Bronsted acid and a base, whereas the latter is obtained from non-reversible alkylation of the heteroatom thus inducing a formal charge center on the cation. The unitary charge is created on cation by the net addition of R+ or H+ to a heteroatom lone pair and this heteroatom is an integral part of the incipient cation [7], [8]. Most of the research work have been focused on AIL but recently PILs have gain increasing attention [9], [10], [11] due to interesting physical properties [12], [13]. Since, PILs participate in strong hydrogen bonding, which become advantageous for applications such as utilizing PILs for protein stabilization, fuel cell, etc. [14], [15]. Among PILs [16], [17], [18], [19], the new class of ILs based on N-methylpyrrolidone (NMP) containing organic anionic moiety have been recently synthesized and studied so as to overcome limitations such as toxicity, high viscosity and cost associated with other PILs [20], [21].
Water as a solvent or as an impurity is ubiquitous within ILs, so studies on the water-IL interaction have gained extensive interest [22], [23]. The IL-solvent (including water) combinations have shown better performance in CO2 capturing, cellulose dissolution, electrochemistry and catalysis [24], [25], [26], [27]. Results suggests the involvement of both anionic and cationic part of IL in modulating the IL-water interactions [22], [23]. However, most of the studies are conducted on imidazolium based AILs or ammonium based PILs [22], [28], [29], [30], [31], [32]. Recently [33], [34], [35] ILs have also been introduced as new absorbents so as to overcome problems such as thermal instability, high volatility and low system performance shown by organic working fluids in absorption cooling systems. The absolute water miscibility, lowering of partial pressure of water as compared to aqueous LiBr solution and absence of crystal formation are crucial absorbent features for optimizing the coefficient of performance (COP) for IL containing working pair [36].
So, the thermodynamic properties of pure and aqueous/nonaqueous ILs solutions with various molecular solvents (water, methanol, ethanol etc.) needed [19], [37], [38] to be studied for optimizing the suitable IL-solvent combination for targeted applications. For instance, accurate thermodynamic properties of pure and mixture fluids are necessary for the suitable design and optimization of the absorption cooling and/or heating systems [33].
In this regard, we have studied the interactions occurring between pyrolidinium based protic ionic liquids and water employing experimental and computational techniques. The density and speed of sound of three protic ionic liquid (PIL), viz. N-methyl-2-pyrrolidonium formate [NMP][For], N-methyl-2-pyrrolidonium propionate [NMP][Pro] and N-methyl-2-pyrrolidonium pentanoate [NMP][Pen] in water at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15, 323.15 and 328.15) K and at atmospheric pressure have been measured. These experimental data were used to calculate apparent molar volume, Vϕ, and apparent molar isentropic compression, Ks,ϕ. The density functional level of theory (DFT) was also employed to understand the nature of inter- and intra-molecular interactions occurring between ions of PIL with water at different temperatures.
Section snippets
Materials
The provenance of the chemicals used along with their purity and purification method have been mentioned in Table 1. All the chemicals were used as such without further purifications.
Synthesis and characterization of PILs
The N-methylpyrrolidone based PILs namely N-methyl-2-pyrrolidonium formate {[NMP][For]}, N-methyl-2-pyrrolidonium propionate {[NMP][Pro]} and N-methyl-2-pyrrolidonium pentanoate {[NMP][Pen]} have been synthesized by exothermic neutralization of base (N-methylpyrrolidone) with acid (formic or propionic or pentanoic
Volumetric properties
Thermodynamic properties studied by evaluating the partial molar quantities are supportive in describing the structure and properties of binary or ternary solutions, thus these quantities can delivers important information about solute-solvent, solute-solute and solvent-solvent interactions [17]. Moreover, these thermodynamic properties of binary or ternary solution containing ionic liquids and various solvents (including water) are required for chemical process design and optimization, for
Conclusions
Apparent molar volumes, Vϕ and apparent molar isentropic compressibilities, Ks,ϕ of three newly synthesized NMP based PILs as function of concentration and temperature has been calculated from experimentally measured density and speed of sound. Infinite dilution partial molar volumes (Vϕ∞ and Kϕ∞) have also been calculated by employing Redlich-Mayer type of equation. Both (Vϕ∞ and Kϕ∞) values increase with increase in temperature as well as with anionic chain length of PILs. Empirical Sv
Acknowledgements
The authors are grateful to IIT Madras for financial support, through Institute Research and Development Award (IRDA): CHY/15-16/833/RFIR/RAME.
References (60)
- et al.
Room temperature ionic liquids and their mixtures−a review
Fluid Phase Equilib.
(2004) Extraction of noble metal ions from aqueous solution by ionic liquids
Fluid Phase Equilib.
(2012)- et al.
Ammonium ionic liquids as green solvents for drugs
Fluid Phase Equilib.
(2013) - et al.
Effect of ionic liquids as adjuvants on PEG-based ABS formation and the extraction of two probe dyes
Fluid Phase Equilib.
(2014) - et al.
Volumetric and ultrasonic properties of ternary (sucrose+ water+ protic ionic liquid) solutions
J. Chem. Thermodyn.
(2015) - et al.
Toward protic ionic liquid and organic ionic plastic crystal electrolytes for fuel cells
Electrochim. Acta
(2012) - et al.
Exploring the thermal stability of α-chymotrypsin in protic ionic liquids
Proc. Biochem.
(2013) - et al.
Thermodynamic properties of aqueous solutions of two ammonium-based protic ionic liquids at 298.15 K
J. Mol. Liq.
(2013) - et al.
Apparent molar properties of benzyldimethylammonium based protic ionic liquids in water and ethanol at different temperatures
Fluid Phase Equilib.
(2015) - et al.
Solvation behavior of monosaccharides in aqueous protic ionic liquid solutions: volumetric, calorimetric and NMR spectroscopic studies
Fluid Phase Equilib.
(2016)
Measurement and correlation for the thermophysical properties of novel pyrrolidonium ionic liquids: effect of temperature and alkyl chain length on anion
Fluid Phase Equilib.
Thermodynamics of hydrogen bonding and van der Waals interactions of organic solutes in solutions of imidazolium based ionic liquids: “Structure-property” relationships
Thermochim. Acta
Water as an efficient medium for the synthesis of cyclic carbonate
Tetrahedron Lett.
Excess molar volumes of binary mixtures (an ionic liquid + water): a review
J. Chem. Thermodyn.
Thermodynamic analysis of an absorption refrigeration system with ionic-liquid/refrigerant mixture as a working fluid
Energy
Thermodynamic properties of new heat pump working pairs: 1,3-dimethylimidazolium dimethylphosphate and water, ethanol and methanol
Fluid Phase Equilib.
Apparent molar volume and apparent molar isentropic compressibility for the binary systems {methyltrioctylammoniumbis (trifluoromethylsulfonyl) imide + ethyl acetate or ethanol} at different temperatures under atmospheric pressure
Thermochim. Acta
A new hybrid exchange–correlation functional using the coulomb-attenuating method (CAM-B3LYP)
Chem. Phys. Lett.
Electrostatic interaction of a solute with a continuum. A direct utilizaion of AB initio molecular potentials for the prevision of solvent effects
Chem. Phys.
Density, speed of sound, and electrical conductance of ionic liquid 1-hexyl-3-methyl-imidazolium bromide in water at different temperatures
J. Chem. Thermodyn.
Apparent molar volume and isentropic compressibility of ionic liquid 1-butyl-3-methylimidazolium bromide in water, methanol, and Ethanol at T = (298.15 to 318.15)
K. J. Chem. Thermodyn.
Volumetric, acoustic and transport properties of binary mixtures of benzyldimethylammonium based ionic liquids with N, N-Dimethylformamide at temperature from 293.15 to 328.15 K
J. Mol. Liq.
Apparent molar properties of hydroxyethyl ammonium based ionic liquids with water and ethanol at various temperatures
J. Mol. Liq.
Apparent molar properties of benzyldimethylammonium based protic ionic liquids in water and ethanol at different temperatures
Fluid Phase Equilib.
Volumetric properties of ionic liquid 1,3-dimethylimidazolium methyl sulfate + molecular Solvents at T = (298.15–328.15) K
Fluid Phase Equilib.
Implicit and explicit solvent models to understand the d(+)-glucose solvation in aqueous protic ionic liquid solution: volumetric and computational approach
J. Chem. Thermodyn.
Ultrasonic velocities and isentropic compressibilities of some symmetrical tetraalkylammonium salts in N,N-Dimethylacetamide at 298.15 K
J. Mol. Liq.
Applications of ionic liquids in the food and bioproducts industries
ACS Sustain. Chem. Eng.
Applications of ionic liquids in the chemical industry
Chem. Soc. Rev.
Interactions in Water−Ionic liquid mixtures: comparing protic and aprotic systems
J. Phys. Chem. B
Cited by (14)
Prospects of MXene and graphene for energy storage and conversion
2024, Renewable and Sustainable Energy ReviewsNovel berberine-based pharmaceutical salts with fatty acid anions: Synthesis, characterization, physicochemical properties
2022, Journal of Molecular LiquidsIonic liquid-nanoparticle based hybrid systems for energy conversion and energy storage applications
2022, Journal of the Taiwan Institute of Chemical EngineersCitation Excerpt :The biological properties of NPs were different when compared with those of bulk materials, moreover, these properties become distinct as the NPs were dispersed from polar to non-polar or buffer or in ILs [60]. ILs can be hydrophobic or hydrophilic, nonetheless, hydrophilic ILs can be considered comparatively safe or to use biocompatible ILs [178–181,182]. The type of interactions between NPs and IL can also leads to toxicity and more studies are needed to resolve this issue [58].
Studies on synthesis, volume and conductivity behaviors of three novel pharmaceutical salts [C<inf>n</inf>Py][AceSA] (n = 8, 10, 12)
2021, Journal of Molecular Liquids