Imidazolium Tetrafluoroborate Research Articles

Abstraction of Trifluoroborane from Tetrafluoroborate: Li+‐Assisted Borylation of Nucleophilic Carbenes

AbstractThe small, lipophilic tetrafluoroborate anion is ubiquitous in the imidazol(in)ium and iminium precursors to N‐heterocyclic carbenes (NHCs), including cyclic (alkyl)(amino)carbenes (CAACs). Its symmetrical distribution of charge over four highly electronegative fluorine atoms confers high stability, attenuating basicity while shielding the boron center. Here we report that this inertness does not withstand the nucleophilicity of free carbenes, when combined with a polarizing lithium cation. Reaction of CAAC ⋅ HBF4 salts with LiN(SiMe3)2, a protocol widely used to liberate free CAACs, generates zwitterionic CAAC‐BF3 adducts within minutes at 80 °C, or hours at room temperature, even for bulky N‐diisopropylphenyl (DIPP) CAACs. Imidazol(in)ium tetrafluoroborates likewise form NHC‐BF3 adducts in excellent yields.

Modulation of Triton X-100 Aqueous Micelle Interface by Ionic Liquid: A Molecular Level Interaction Studied by Time-resolved Fluorescence Spectroscopy

Background: Self-assembly structure is an important area of research for understanding biological systems, owing to its resemblance to the membrane structure of the phospholipid bilayer. In a self-assembly medium, chemical reactions and chemical or physical processes are dramatically different than the bulk phase. Understanding this process in synthesizing self-assembly structures may allow us to explore various biological processes occurring in cell membranes. Objective: The study aimed to understand water dynamics in the TX-100 micellar interface via steady state and a time-resolved fluorescence spectroscopy study. The objective was also to determine the two different ionic liquids (ILs), namely 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim][BF4]) and 1-decyl-3-methyl imidazolium tetrafluoroborate ([dmim][BF4]), inducing surfactant aggregation changes at the molecular level. Also, the focus was on determining the hydration and its dynamics at the palisade layer of TX-100 micelle in the presence of two different ionic liquids. Methods: Steady state and time-resolved fluorescence spectroscopy have been used to study TX-100 micellar systems. Employing time-resolved spectroscopy, two chemical dynamic processes, solvation dynamics and rotational relaxation dynamics, have been studied to investigate structural changes in TX100 by adding ILs. Solvation dynamics was studied by measuring the time-dependent Stokes shift of the fluorescent probe. From the Stokes shift, time-resolved emission spectra were constructed to quantify the solvation dynamics. Also, using the polarization properties of light, time-resolved anisotropy was constructed to explore the rotation relaxation of the probe molecule. Results: The absorption and emission spectra of C-153 in TX-100 were red-shifted in the presence of both the ILs. Also, the C-153 experienced faster solvation dynamics and rotational relaxation with the addition of both ILs. In our previous study, we observed a significantly increased rate of solvation dynamics with the addition of [bmim][BF4] (J. Phys. Chem. B, 115, 6957-6963) [38]. However, with the addition of the same amount of [dmim][BF4], the IL rate of solvation enhancement was more pronounced than with [bmim][BF4]. The faster solvation and rotational relaxation have been found to be associated with the penetration of more free water at the TX100 micellar stern layer, leading to increased fluidity of the micellar interface. Conclusion: Upon incorporating ILs in TX100 micelle, substantially faster solvation dynamics of water as well as rotational relaxation dynamics of C-153 have been observed. By decreasing surfactant aggregations, [bmim][BF4] ILs facilitated more water molecules approaching the TX-100 micellar phase. On the other hand, [dmim][BF4] ILs comprising mixed micelles induced even more free water molecules at the palisade layer, yielding faster solvation dynamics in comparison to pure TX-100 micelle or TX100 micelle + [bmim][BF4] ILs systems. Time-resolved anisotropy study has also supported the finding and strengthened the solvation dynamics observation.

How to Control Excited‐State Prototropism of Photoacids via the Acidity of Ionic Liquids

AbstractTo control presence of ionic species in excited state of a fluorophore is quite challenging task. Herein, we report the unusual excited‐state prototropism of an important photoacid carbazole dissolved in water in presence of small amount of added ionic liquids (ILs). We have observed that the excited state prototropic equillibria of carbazole dissolved in water can be affected by the presence of small amount of added ILs. More importantly, the excited‐state prototropism of carbazole can be controlled via the acidity of added ILs. More specifically, we found that the fluorescence emission from the neutral prototropic form of carbazole can be observed even under highly basic conditions (aqueous NaOH, pH 12.6) in presence of only small amount of any of the added ILs such as 1‐butyl‐3‐methyl imidazolium tetrafluoroborate ([bmim][BF4]), 1‐butyl‐1‐methylpyrrolidinium bis(trifluromethansulphonyl)imide ([bmpyrr][Tf2N]) and 1‐butyl‐3‐methyl imidazolium hexafluorophosphate ([bmim][PF6]). The observed fluorescence emission from the neutral form of carbazole can be attributed to excited state protonation of carbazole anion by taking proton from IL cation. In a true sense, the excited state carbazole does not transfer the proton; rather takes the proton from IL cation. The observed unusual excited state protonation of carbazole anion to neutral carbazole, in the excited state even in highly basic conditions can be attributed to the presence of acidic protons with the IL cations. Herein, we reports quite unusual results where the IL assisted excited state protonation of carbazole anion occured in an exclusive manner in which proton from the IL cation exclusively protonate carbazole anion surrounded by highly alkaline media (water, pH 12.6). ILs acidity controlled excited‐state properties of important photoacids can have a wide range of chemical and biological applications and the observed results can play important roles in chemical technology to control prototropic equillibra with the help of ILs for some specific application. These observations can open new windows to attract more applications for these alternative solvent media to applications in pH and pOH jump experiments, effective photo protecting agents and chemical lasers.

Economically Viable Process for Synthesizing and Purifying Ionic Liquids: 1-Butyl-3-methyl Imidazolium Tetrafluoroborate

Economically Viable Process for Synthesizing and Purifying Ionic Liquids: 1-Butyl-3-methyl Imidazolium Tetrafluoroborate

Structure-Dependence and Mechanistic Insights into the Piezoelectric Effect in Ionic Liquids.

We reported recently that two imidazolium room-temperature ionic liquids (RTILs) exhibit the direct piezoelectric effect (J. Phys. Chem. Lett., 2023, 14, 2731-2735). We have subsequently investigated several other RTILs with pyrrolidinium and imidazolium cations and tetrafluoroborate and bis(trifluoromethylsulfonyl)imide anions in an effort to gain insight into the generality and mechanism of the effect. All the RTILs studied exhibit the direct piezoelectric effect, with a magnitude (d33) and threshold force that depend on the structures of both the cation and anion. The structure-dependence and existence of a threshold force for the piezoelectric effect are consistent with a pressure-induced liquid-to-crystalline solid phase transition in the RTILs, and this is consistent with experimental X-ray diffraction data.

Molecular simulations of understanding the structure and separation thermodynamics of 5-Hydroxymethylfurfural from 1-Butyl-3-Methyl imidazolium tetrafluoroborate

The furfural-based compounds derived from biomass is proven to be reducing greenhouse gas emissions for sustainable chemical processes. 5-hydroxymethylfurfural (5-HMF) is a bio-renewable material that can serve as a significant platform chemical to produce biofuels, green polymers, solvents, etc. Ionic liquids (ILs) have shown promising reaction media to produce 5-HMF from glucose and fructose. However, there is a substantial challenge in separating the 5-HMF from the ILs. In this paper, we use an organic solvent tetrahydrofuran (THF) to understand the molecular level properties of 5-HMF from 1-butyl-3-methyl imidazolium tetra-fluoroborate [BMIM]+[BF4]− using all-atom molecular dynamics simulations. We have analyzed various intermolecular structures, and dynamic and separation thermodynamic properties. Our results show that with an increase in 5-HMF concentration, we observe a favorable intermolecular interaction between 5-HMF and THF compared to the interactions between 5-HMF and [BMIM]+. The 5-HMF presents the dominant intermolecular interactions with cations compared to the anions. The self-diffusion coefficient of 5-HMF shows a decrease in THF and an increase in [BMIM]+[BF4]− with the rise in 5-HMF concentration. The solvation free energy (ΔGsolv) values of 5-HMF in both IL and THF show less negative value with an increase in 5-HMF concentration. The transfer free energy (ΔGtransfer) of 5-HMF (from IL to THF) shows less positive values with an increase in 5-HMF concentration. Overall results presented in this work are promising for understanding the complex interactions between furfural-based compounds and ILs.

Study on the thermal decomposition of an ionic liquid propellant [EMIm][BF4

Ionic liquids are regarded as promising propellants for green spacecraft propulsion. A well understanding of their fundamental properties is essential to accelerate the applications in practical propulsion. Therefore, the decomposition properties of an imidazole-based ionic liquid 1-ethyl-3-methyl imidazolium tetrafluoroborate ([EMIm][BF4]) were studied in this paper to help evaluate its chemical propulsion performance. Decomposition experiments were carried out with a high-temperature integrated thermal analyzer with heating rates of 5–20 °C/min. Results showed the decomposition process can be divided into four stages by three characteristic temperatures. The mass loss and heat absorption mainly occurred in the second and third stages. The activation energy of decomposition reactions was also obtained. Analyses indicated mechanisms in the first and second stages are multiple-step kinetics. But that of the third and fourth stages can be simplified as single-step kinetics.

On revealing structural relaxation of ionic liquids by high-field dielectric techniques

Using dielectric relaxation techniques at low and high electric fields, it is demonstrated how the conductivity and structural relaxation times can be obtained under identical sample conditions, e.g., for ionic liquids. This approach is useful for conductive materials for which low field dielectric loss spectra fail to display signatures of structural relaxation. The approach is based on field induced structural recovery in the regime of milliseconds, i.e., the process of fast physical aging in response to a small perturbation. For the case of viscous 1‑butyl‑3-methyl imidazolium tetrafluoroborate, this experiment reveals a decoupling quantified by structural relaxation being about nine times slower than conductivity relaxation.

A novel phase change absorbent with ionic liquid as promoter for low energy-consuming CO2 capture

Phase change absorbents had great potential to achieve low energy-consuming CO2 capture. In this work, a novel four-component phase change absorbent system, N,N-diethylethanolamine (DEEA)/N-(2-aminoethyl) ethanolamine (AEEA)/1-butyl-3-methyl imidazolium tetrafluoroborate ([Bmim][BF4])/H2O blends, was designed. AEEA and DEEA were used as the main absorption component and the phase separation component, respectively. As one of the most conventional ionic liquids, [Bmim][BF4] was introduced as a promoter to improve the phase separation capability and the absorption/desorption performance. The species distribution was determined by 13C NMR analysis, and it was found that [Bmim][BF4] was located in the lower phase. Quantum chemical calculations unveiled that the main reason for phase separation was the difference in polarity and hydrogen bond interactions. The introduction of the [Bmim][BF4] not only promoted CO2 absorption through chemical and physical intensification effects but also enhanced the desorption rate through hydrogen bond formation. Moreover, the [Bmim][BF4] addition significantly reduced regeneration energy consumption due to its lower heat capacity and less water evaporation. The energy consumption of this absorbent could be reduced to 2.06 GJ∙t−1 CO2, which was 45.8% less than 30 wt% MEA.

Investigation of Molecular Mechanism of Cobalt Porphyrin Catalyzed CO2 Electrochemical Reduction in Ionic Liquid by In-Situ SERS.

This study explores the electrochemical reduction in CO2 using room temperature ionic liquids as solvents or electrolytes, which can minimize the environmental impact of CO2 emissions. To design effective CO2 electrochemical systems, it is crucial to identify intermediate surface species and reaction products in situ. The study investigates the electrochemical reduction in CO2 using a cobalt porphyrin molecular immobilized electrode in 1-n-butyl-3-methyl imidazolium tetrafluoroborate (BMI.BF4) room temperature ionic liquids, through in-situ surface-enhanced Raman spectroscopy (SERS) and electrochemical technique. The results show that the highest faradaic efficiency of CO produced from the electrochemical reduction in CO2 can reach 98%. With the potential getting more negative, the faradaic efficiency of CO decreases while H2 is produced as a competitive product. Besides, water protonates porphyrin macrocycle, producing pholorin as the key intermediate for the hydrogen evolution reaction, leading to the out-of-plane mode of the porphyrin molecule. Absorption of CO2 by the ionic liquids leads to the formation of BMI·CO2 adduct in BMI·BF4 solution, causing vibration modes at 1100, 1457, and 1509 cm-1. However, the key intermediate of CO2-· radical is not observed. The υ(CO) stretching mode of absorbed CO is affected by the electrochemical Stark effect, typical of CO chemisorbed on a top site.

Unraveling abnormal buried interface anion defect passivation mechanisms depending on cation-induced steric hindrance for efficient and stable perovskite solar cells

Although ionic liquids (ILs) have been widely employed to heal the defects in perovskite solar cells (PSCs), the corresponding defect passivation mechanisms are not thoroughly understood up to now. Herein, we first reveal an abnormal buried interface anion defect passivation mechanism depending on cation-induced steric hindrance. The IL molecules containing the same anion ([BF4]-) and different sizes of imidazolium cations induced by substituent size are used to manipulate buried interface. It was revealed what passivated interfacial defects is mainly anions instead of cations. Theoretical and experimental results demonstrate that the large-sized cations can weaken the ionic bond strength between anions and cations, and facilitate the interaction between anions and SnO2 as well as perovskites, which is conducive to interfacial defect passivation and ameliorating interfacial contact. It can be concluded that interfacial chemical interaction strength and defect passivation effect are positively correlated with the size of cations. The discovery breaks conventional thinking that large-sized modification molecules would weaken their chemical interaction with perovskite. Compared with the control device (21.54%), the device based on 1,3-Bis(1-adamantyl)-imidazolium tetrafluoroborate (BAIMBF4) with maximum size cations achieves a significantly enhanced efficiency of 23.61% along with much increased moisture, thermal and light stabilities.

Experimental investigation on the thermophysical properties of the ionic liquid-based binary system for heat transfer applications

Based on the innovation in the development of ionic liquids, the aim of the present work is to investigate the thermophysical properties of novel hydrophilic ionic liquid 1-Ethyl-3-Methyl Imidazolium Tetra FluoroBorate (EMIMBF4) and water as binary systems experimentally at various mass fraction and at various temperatures. A room-temperature ionic liquid blended with deionized water in four different mass fractions as 20%, 15%, 10%, and 5% to prepare an ionic liquid and water binary mixture at room temperature. Thermal stability and the thermophysical characteristics of EMIMBF4 such as thermal conductivity, specific heat capacity, viscosity, and density, were measured in the temperature range of 25?C to 90?C. The results reveal that the specific heat capacity increased by 13%, and thermal conductivity enhanced 9%, at 5 wt.% mass fraction. The overall mass drop is reached 75.1% at 20 wt.% mass fractions.

Zwitterionic ionic liquid synergistically induces interfacial dipole formation and traps state passivation for high-performance perovskite solar cells

Defects at the interface and grain boundaries of perovskite solar cells (PSCs) will result in severe non-radiative recombination and open-circuit voltage (Voc) loss. Herein, we reported a zwitterionic ionic liquid imidazolium tetrafluoroborate (IMBF4) to passivate the defects at tin dioxide (SnO2)/perovskite interface. The results showed that the electron-rich nitrogen atom contained IM+ could diffuse into the buried perovskite to exhibit a strong chemical passivation effect on the organic vacancy defect by interacting with uncoordinated Pb2+. The F– in BF4- has a strong coordination effect with Pb2+in perovskite and Sn2+ in SnO2 synchronously to fill the anion vacancy defect. Also, the BF4- anions could help to form an interface dipole layer to increase the charge transfer rate and reduce the work function. The IMBF4 modified device could achieve an efficiency enhancement from 20.18% to 23.05% by vacuum flash-assisted solution-processed, with the increased Voc from 1.09 V to 1.15 V. The unencapsulated IMBF4 modified device could maintain 93% of the initial efficiency after ageing for 2000 h under ambient conditions by the ISOS-D-1 stability-testing protocols. This work emphasizes the importance of multifunctional additives in passivating defects and improving interface contact for achieving efficient and stable perovskite solar cells.

Remediation of wastewater containing 4-nitrophenol using ionic liquid stabilized nanoparticles: Synthesis, characterizations and applications.

In the present study, an ionic liquid (IL) based on 1-butyl-3- (trimethoxysilylpropyl) -imidazolium tetrafluoroborate (IL) was prepared using metathesis and anion exchange reactions and used to stabilize silver (AgNPs) nanoparticles. The IL-stabilized silver nanoparticles AgNPs@[BMSI]BF4 were produced in an aqueous solution with NaBH4 as a reducing agent. TGA, FTIR, XRD, BET, FSEM, TEM/HRTEM, XPS, and UV-Vis spectra were used to analyze AgNPs@[BMSI]BF4 and were used for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4. AgNPs@[BMSI]BF4 showed excellent catalytic properties for the reduction of 4-NP to 4-AP and showed 100% conversion of 4-NP to 4-AP within 6min and the rate constant (k) was found to be 8.33×10-3 s-1. The reusability results indicated that 97.8% of 4-NP was converted to 4-AP with highly stable rate constants over six consecutive cycles. The activity factor (AF) and the turn-over frequency (TOF) at room temperature were 3.33 s-1 gm-1 and 0.166 s-1, respectively. This study extends a new approach to the production of stable catalysts for the growing needs in wastewater treatment.

Green synthesis of ionic liquid mediated neodymium oxide nanoparticles via Couroupita guianensis abul leaves extract with its biological applications

Bio-nanoparticles have created a new era of rapid, harmless and nontoxic drugs for various biomedical applications. The nanoparticles (NPs) of rare earth metal oxides attract researcher’s attention due to their excellent chemical and physical properties that exhibit potential activity against disease causing pathogens. Couroupita guianensis (C. guianensis) abul is a medicinal plant whose leaves are effectively used for the synthesis of neodymium oxide (Nd2O3) NPs. The 1-butyl 3-methyl imidazolium tetrafluoroborate (BMIM BF4) ionic liquid is used as a stabilizing agent to get better the morphology and biological properties of Nd2O3 NPs. 1-Butene, 4,4-diethoxy-2-methyl is the main compound in C. guianensis abul leaves extract was confirmed by GCMS analysis. The structure of synthesized Nd2O3 (without ionic liquid) and Nd2O3-IL (with ionic liquid) NPs is identified by powder X-ray diffraction (PXRD). The vibrations of the different functional groups were investigated by Fourier-transform infrared (FTIR) and Raman spectroscopy. In UV–Vis spectra, the optical absorption was identified to be 210 and 221nm of Nd2O3 and Nd2O3-IL samples and the PL spectrum provides blue and green emission peaks at 386 and 554 nm. The X-ray photoelectron spectroscopy (XPS) and DLS spectra illustrate the electronic configuration and particle size of the synthesized Nd2O3-IL NPs. The morphology, surface nature and lattice spacing were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The purity and weight percentage of the compound presented can be identified by the energy-dispersive X-ray spectroscopy (EDX). The biomedical properties such as antibacterial, antioxidant, antidiabetic, anti-inflammatory and anticancer activities were investigated. Finally, the overall biocompatible studies reveal that the ionic liquid assisted Nd2O3 NPs can be considered as a potential drug for pharmaceutical and biomedical applications.

Ion Specific, Thin Film Confinement Effects on Conductivity in Polymerized Ionic Liquids

Acrylate-based polymerized ionic liquids (PILs) with ammonium (Am) or imidazolium (Im) cations and tetrafluoroborate (BF4) or bis(trifluoromethanesulfonyl)imide (TFSI) anions were synthesized and s...

Solvatochromic probes behaviour within ternary room temperature 1-butyl-3-methyl imidazolium tetrafluoroborate + methanol + water solutions

The study of the solvent–solvent and solute–solvent interaction within Ionic Liquid based binary and ternary mixture is a key to understand the molecular level behaviour of these solvents, which will further render the utilization of these neoteric solvents in several important applications. In this study, we applied invasive and non-invasive approach to understand the molecular level insight of ternary mixture of the ionic liquid (IL) 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim][BF4]) with water (H2O) and methanol (MeOH). We used UV–visible, fluorescense, and Fourier transform infrared (FTIR) techniques to investigate the effect of methanol on the structural organization of aqueous solutions of IL. The Solvatochromic probes are used to study the solvation behaviour of ternary mixture of [bmim][BF4] + MeOH + H2O. Interestingly the values of the polarity parameter [ET(30)] are higher for various compositions of the ternary system consists of [bmim][BF4] + MeOH + H2O than in neat [bmim][BF4] or aqueous methanol. The dipolarity/polarizability (π*) values of ternary [bmim][BF4] + MeOH + H2O solutions are even greater than those in neat ionic liquid or aqueous methanol. While higher hydrogen bond donating “α“ value is observed in ternary mixture than that of neat IL or aqueous methanol. The findings here clearly demonstrate that addition of aqueous methanol to [bmim][BF4], modulate the physicochemical properties of the IL in interesting and favourable manner.

Density, Speeds of Sound, and Refractive Index of Pure and Binary Mixtures of Ionic Liquids Based on Imidazolium Cations and Tetrafluoroborate Anions with Cyclohexylamine

Density, Speeds of Sound, and Refractive Index of Pure and Binary Mixtures of Ionic Liquids Based on Imidazolium Cations and Tetrafluoroborate Anions with Cyclohexylamine

Relation between ionic surfactant concentration and thickness of foam film stabilized by ionic – nonionic surfactant mixed adsorbed films

In this paper, we compared the thickness of common black films stabilized by four different ionic-nonionic surfactant mixed adsorbed films. For the cetyltrimethylammonium chloride (CTAC) - pentaethyleneglycol monododecyl ether (C12E5), SDS - tetraethyleneglycol monodecyl ether (C10E4), and dodecyltrimethylammonium bromide (DTAB) - tetraethyleneglycol monooctyl ether (C8E4) systems, the foam film thickness measured by using Scheludko–Exerowa glass ring method coincided very well when the foam film thickness was plotted as a function of bulk ionic surfactant (1:1 electrolyte) concentration. In addition, by using the phase diagram of mixed adsorbed film obtained from the thermodynamic analysis of the surface tension data, it was also demonstrated that the surface charge density and surface tension have a minor effect on the equilibrium film thickness. On the other hand, the foam film stabilized by the 1-decyl-3-methyl imidazolium tetrafluoroborate (DMIMBF4) - C10E4 mixed adsorbed film showed much smaller thickness values compared to the above-mentioned systems. Irregular behavior observed in the DMIMBF4 - C10E4 system was discussed based on the specific interaction between imidazolium head groups and BF4- ions through hydrogen bonding in an ion-concentrated environment in the Stern layer.

Synthesis and characterization of the ionic liquid 1-methyl-3-(2,6-(S)-dimethyloct-2-ene)-imidazol tetrafluoroborate

Ionic liquids (ILs) are good electrical conductors and organic liquid compounds at room temperature, with potential applicability in water electrolysis for H2 generation. The objective of this work is to describe the synthesis, characterization and study of the feasibility of ionic liquid 1-methyl-3-(2,6-(S)-dimethyloct-2-ene)-imidazolium tetrafluoroborate (MDI-BF4) as electrolyte to produce hydrogen through electrolysis of water. The synthesized MDI-BF4 was characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), mid-infrared spectroscopy with Fourier Transform by method of attenuated total reflectance (FTIR-ATR), nuclear magnetic resonance spectroscopy of hydrogen (NMR 1H) and cyclic voltammetry (CV). The yield of the synthesis were calculate by the TGA and DSC. From the results: The infrared spectroscopy identified the functional groups of the compound and the B-F bond at 1053 cm-1. The NMR 1H analyzed and compared with literature data confirms the structure of MDI-BF4. The yield of the synthesis of MDI-BF4 which was 88.84%. The current density achieved by MDI-BF4 in the voltammogram shows that the IL can conduct electrical current regardless the concentration of water, indicating that the MDI-BF4 is a potential electrolyte for hydrogen production from water electrolysis.