Molecular Assembling in Mixtures of Hydrophilic 1-Butyl-1-Methylpyrrolidinium Dicyanamide Ionic Liquid and Water

Abstract

The infrared absorbance spectrum of the ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide, mixed with water at two different concentrations, was measured between 160 and 300 K in the mid infrared range. Both mixtures do not crystallize on cooling; however, remarkably, the one with an ionic liquid (IL):water composition of 1:3 displays a cold crystallization process on heating in a restricted temperature range between 240 and 250 K. A portion of the water participates to the cold crystallization. On the contrary, with an IL:water composition of 1:6.6 no crystallization takes place. Upon water addition the vibration frequencies of the anion and of some lines of the cation are blue shifted, while the absorption lines of water are red shifted. These facts are interpreted as the evidence of the occurrence of the hydrogen bonding of water, as the hydrogen bonding acceptor with respect to the anion (anion∙∙∙O-H bonds develop) and as hydrogen donor for the cation (C-H∙∙∙O bonds can form). Microscopic inhomogeneities in the samples and their evolution with temperature are discussed.

An Integrated Computational–Experimental Hierarchical Approach for the Rational Design of an IL/UiO‐66 Composite Offering Infinite CO2 Selectivity

“…[ 22 ] Meanwhile, the obvious strong IR bands at 1306, 2129, 2190, and 2230 cm –1 in the IR spectrum of the bulk IL are associated with the NC mode vibrations of the [DCA] − anion. [ 23 ] Moreover, those at 2875 and 2964 cm –1 are associated with the symmetric and asymmetric C−H stretching vibrations of the IL cation. Hence, these shifts in the IR features associated with the MOF and the IL's anion verify the existence of interactions between the two moieties in the composite material.…”

Composite of MIL-101(Cr) with a Pyrrolidinium-Based Ionic Liquid Providing High CO2 Selectivity

“…To have a better understanding of these molecular IL-MOF interactions, we compared the IR spectrum of the [MPPyr]­[DCA]/MIL-101­(Cr) composite with those of MIL-101­(Cr) and the bulk [MPPyr]­[DCA], as shown in Figure a,b. The IR features at 2881 and 2972 cm –1 in the spectrum of the bulk [MPPyr]­[DCA] are assigned to the symmetric and asymmetric ν­(C–H) vibrations, and those at 1301, 2123, 2189, and 2223 cm –1 are attributed to ν­(CN) on [DCA] − . , Figure demonstrates that the ν­(CN) bands located at 2123 and 2223 cm –1 blue-shifted by 14 and 11 cm –1 , respectively, when the IL molecules were incorporated into the pores. These shifts were accompanied by a blue shift of 9 cm –1 on the ν­(C–H) peak of the IL positioned at 2881 cm –1 .…”

Binary Mixtures of Choline Acetate and Tetrabutylammonium Acetate with Natural Organic Acids by Vibrational Spectroscopy and Molecular Dynamics Simulations

“…69 Also, those authors attributed the red shift of S�O bands and the blue shift of OH bands to the hydrogen bond network present in the mixtures. Shifts of the infrared bands due to variations of the hydrogen bonds have been reported in some ionic liquids in the presence of solvents, 67,70 such as water. The band frequency shift was higher in ionic liquids mixed with water in the case that the ILs were protic, i.e., they already contained hydrogen bonds between anions and cations: shifts of ∼12 cm −1 were reported in the case of protic N-methyl-2-pyrrolidonium propionate, to be compared to values of about 6 cm −1 for aprotic cholinium propionate.…”