Local Structures of Water in 1-Butyl-3-methylimidazolium Tetrafluoroborate Probed by High-Pressure Infrared Spectroscopy

Abstract

We have investigated the aggregation behaviors of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate/ water mixtures using high-pressure methods. Under ambient pressure, the IR spectra indicate that two types of O-H species:freeO-HandbondedO-H,existinginionicliquid/watermixtures.Assampleswerecompressed,acontinuous lossofthefreeO-Hbandintensitywasobserved.Thisobservationmayhavearisenfromchangesinthelocalstructures of water molecules, and the geometrical properties of the hydrogen-bond network are likely to be perturbed as the pressureiselevated.AcomplementaryinsightoftheO-Hspectralfeaturesisobtainedbymeasuringtheconcentrationdependent variation in the mid-infrared spectra under high pressure. A sharp O-H stretching band was observed in a dilutedmixturecorrespondingtothehighorderinaniceVII-likestructure.Nevertheless,averybroadO-Hfeaturewas measuredinaconcentratedmixture,whichmaybeattributedtothepresenceofmorethanonestablecluster.

Synthesis, Crystal Structures and Characterization of Two Nonmetal Cation Tetrafluoroborates

“…C-N and C-C aliphatic groups stretching bands are observed in the range 1220-1020 cm −1 [33]. These results are in good agreement with the literature [34,35].…”

High Pressure Phase Behavior of Two Imidazolium-Based Ionic Liquids, [bmim][BF4] and [bmim][PF6]

“…Generally, RTILs are classified into several groups depending on the cationic series, imidazolium, pyridinium, and alphatic quaternary ammonium series. Most of studies so far concern with the results at atmospheric pressure, but recently an increasing number of works using high pressure is reported (Chang et al, 2007(Chang et al, , 2008a(Chang et al, , 2008b(Chang et al, , 2008cSu et al, 2009Su et al, , 2010Umebayashi et al, 2009aUmebayashi et al, , 2009b. A merit of the use of high pressure as a varialbe is summarized as follows.…”

“…We wonder that the conformational analysis of [bmim] cation under high pressure is necessary to obtain the structural information of the high pressure phase behavior of the RTIL in relation to the packing efficiency. Actually, the solution structures including the conformational behavior o f R T I L s h a v e b e e n s t u d i e d t o r e v e a l t h e physical and chemical properties such as conductivity, viscosity, and melting point (Chang et al, 2007(Chang et al, , 2008cNishikawa et al, 2008Nishikawa et al, , 2009Rivera-Calzada et al, 2008;Seki et al, 2009). The remainder of the paper is organized as follows.…”

Solvatochromic polarity parameters for binary mixtures of 1-butyl-3-methylimidazolium acetate with water, methanol, and dimethylsulfoxide

“…The obtained results agree with the data from studying the interactions between 1-butyl-3methylimidazolium cations and water molecules [29] and can be explained by the ability of [BMIm] + ions to form [BMIm (H 2 O) 4 ] + hydrates. This results in the retention of a pure ionic liquid's supramolecular structure, which is typical of cationic surfactants with short alkyl chains and includes clusters in which a molecular solvent interacts only with the ionic liquid over a broad range of mixture compositions [30,31]. At contents of water above 80 mol %, a network of hydrogen bonds is formed between its molecules when the liquid transitions to an ice-like structure and its physicochemical characteristics approach values typical of aqueous solutions.…”

“…Different solvatochromic parameters determined from the data on N T E PHYSICAL CHEMISTRY OF SOLUTIONS the location of bands in the absorption (emission) spectra of standard compounds (solvatochromic indicators), in which the energy of electron transitions is determined by certain properties of a medium, are now most often used for the quantitative characterization of such properties [20][21][22]. This is especially true of the Dimroth-Reichardt energy E T (30), determined for the electron transition of N-4-oxy-3,5-diphenyl-2,4,6-triphenylpyridinium betaine (Reichardt betaine) and now serving as a generalized medium polarity characteristic, and the Kamlet-Taft solvatochromic parameters α, β, and π* [20][21][22][23][24][25][26][27], which reflect the electron-accepting and electron-donating ability of a solvent and its polarity/polarizability, respectively. The latter are widely used to describe the effect a solvent has on the properties and reactivity of dissolved compounds using the principle of the linear solvation energy relationships (LSER) in the Kamlet-Taft formalism [26]:…”