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Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf2](-)), and dicyanamide {[N(CN)2](-)} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy-derivatized ionic liquids are often crystalline; however, room-temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf2](-) and [N(CN)2](-). For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl-substituted analogues. Of the crystalline compounds, X-ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl-substituted imidazolium salts was shifted to somewhat more positive potentials., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Protonated betaine bis(trifluoromethylsulfonyl)imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium(II) oxide, mercury(II) oxide, nickel(II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese(II) oxide, and silver(I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis(trifluoromethylsulfonyl)imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C (temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis(trifluoromethylsulfonyl)imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.

Manganese(ii)-containing ionic liquids were synthesized, in which the manganese atoms are coordinated by glymes (diglyme, triglyme, tetraglyme), pyridine-N-oxide, dimethylsulfoxide or N-alkylimidazoles (N-methylimidazole, N-butylimidazole and N-hexylimidazole). As anion, bis(trifluoromethanesulfonyl)imide (bistriflimide, Tf2N−), trifluoromethanesulfonate (triflate, OTf−) or methanesulfonate (mesylate, OMs−) were used. The compounds were characterized by CHN analysis, FTIR, DSC and single-crystal X-ray diffraction measurements. All manganese atoms were six-coordinate. It was found that the glyme-type ligands were replaced by atmospheric water upon leaving the crystals open to the air for several days. The crystal structures of seven compounds were described in detail and the compounds with the lowest melting temperatures were tested as electrolytes for the electrodeposition of manganese (thin) films. An irreversible reduction wave from Mn(ii) to Mn(0) and granular manganese deposits were observed for all compounds, except for liquid manganese salts with N-alkylimidazole ligands and bistriflimide anions, where the electrochemical formation of manganese nanoparticles was observed instead of the deposition of a manganese layer. However, for compounds with the same cation but with a triflate or methanesulfonate anion, manganese metal deposits were obtained, indicating that the nature of the anion has an important effect on the electrochemical properties of liquid metal salts. [ABSTRACT FROM AUTHOR]

New nickel-containing ionic liquids were synthesized, characterized and their electrochemistry was investigated. In addition, a mechanism for the electrochemical synthesis of nanoparticles from these compounds is proposed. In these so-called liquid metal salts, the nickel(II) cation is octahedrally coordinated by six N-alkylimidazole ligands. The different counter anions that were used are bis(trifluoromethanesulfonyl)imide (Tf2N−), trifluoromethanesulfonate (OTf−) and methanesulfonate (OMs−). Several different N-alkylimidazoles were considered, with the alkyl sidechain ranging in length from methyl to dodecyl. The newly synthesized liquid metal salts were characterized by CHN analysis, FTIR, DSC, TGA and viscosity measurements. An odd-even effect was observed for the melting temperatures and viscosities of the ionic liquids, with the complexes with an even number of carbon atoms in the alkyl chain of the imidazole having a higher melting temperature and a lower viscosity than the complexes with an odd number of carbons. The crystal structures of several of the nickel(II) complexes that are not liquid at room temperature were determined. The electrochemistry of the compounds with the lowest viscosities was investigated. The nickel(II) cation could be reduced but surprisingly no nickel deposits were obtained on the electrode. Instead, nickel nanoparticles were formed at 100 % selectivity, as confirmed by TEM. The magnetic properties of these nanoparticles were investigated by SQUID measurements. [ABSTRACT FROM AUTHOR]

The ionic liquid choline bis(trifluoromethylsulfonyl)imide, [Chol][Tf2N], was used for the extraction of neodymium(III), in combination with choline hexafluoroacetylacetonate, [Chol][hfac], as the extractant. The binary mixture of [Chol][Tf2N] and water shows temperature-dependent phase behavior, with an upper critical solution temperature of 72 °C. A novel extraction technique, homogeneous liquid-liquid extraction (HLLE), was applied to this solvent system. HLLE is based on the use of thermomorphic solvent mixtures and has the advantage of forming a homogeneous phase during mixing. Extraction is not kinetically hindered by an interface and the extraction equilibrium is reached faster than in the case of heterogeneous mixing in conventional solvent extraction. Several extraction parameters were studied for the extraction of neodymium(III) with [Chol][hfac]: temperature, pH, extractant concentration and loading of the ionic liquid phase. A speciation study was performed to determine the stoichiometry of the extracted neodymium(III) complex and a plausible extraction mechanism is proposed. Neodymium is extracted as a tetrakis hexafluoroacetylacetonate complex with one choline cation as counter ion. The crystal structure of the extracted complex showed the presence of a coordination bond between the choline counter ion and the neodymium(III) center, resulting in a coordination number of nine. The stripping of the loaded neodymium and the influence of acid and extractant concentrations on the phase behavior of the [Chol][Tf2N]-H2O system were investigated. [ABSTRACT FROM AUTHOR]

Metal oxides were found to dissolve in different imidazolium ionic liquids with a hydrogen atom in the C2 position of the imidazolium ring, but not if a methyl substituent was present in the C2 position. The crystal structure of the product that crystallised from an ionic liquid containing dissolved silver(I) oxide showed that this was a silver(I) carbene complex. The presence of carbenes in solution was proven by 13C NMR spectroscopy and the reactions were also monitored by Raman spectroscopy. The dissolution of other metal oxides, namely copper(II) oxide, zinc(II) oxide and nickel(II) oxide, was also studied in imidazolium ionic liquids and it was found that stable zinc(II) carbenes were formed in solution, but these did not crystallise under the given experimental conditions. A crystalline nickel(II) carbene complex could be obtained from a solution of nickel(II) chloride dissolved in a mixture of 1-butyl-3-methylimidazolium and 1-ethyl-3-methylimidazolium acetate. [ABSTRACT FROM AUTHOR]

The synthesis, structure and electrochemical properties of several silver-containing liquid metal salts have been investigated. These ionic liquids comprise of a silver-containing cation with a silver centre coordinated by two or more alkylamine ligands and a bis(trifluoromethylsulfonyl)imide (Tf2N) anion. With the monodentate amines tert-butylamine ( tBuAm), iso-butylamine ( iso-BuAm), sec-butylamine ( sec-BuAm), 2-ethylhexylamine (2-EtHexAm), di(2-ethylhexyl)amine and piperidine (pip), compounds with the formula [Ag(L)2][Tf2N] are formed, several of which are room-temperature ionic liquids and all melt at or below 100 °C. In the case of [Ag(L)2][Tf2N] (L= tBuAm, iso-BuAm and pip), single-crystal X-ray diffraction shows that, in the solid state, the silver centres are two-fold coordinated by two amine ligands and the anion and cation exist as separated ion pairs. With ethylenediamine (en), two different compounds were formed, depending on the silver-to-ligand ratio and their structures were elucidated by X-ray diffraction. [Ag(en)][Tf2N] has a very high melting point and is polymeric in the solid state, with en ligands coordinated to different silver(I) centres, creating one-dimensional chains. [Ag(en)2][Tf2N], on the other hand, is a room-temperature ionic liquid, with four-coordinate silver(I) centres, but is actually polymeric in the solid state. The electrodeposition behaviour of [Ag(2-EtHexAm)2][Tf2N] and [Ag(en)2][Tf2N] was investigated both at room temperature and at 90 °C and it was possible to achieve very high current densities in unstirred solutions and to electrodeposit closed, crack-free, silver coatings. A crystal of [Ag2(en)Cl2] was obtained from a solution of [Ag(en)][Tf2N] in deuterochloroform and its structure is described. [ABSTRACT FROM AUTHOR]

The first palladium-containing Liquid Metal Salts (LMS) are presented and shown to be suitable electrolytes for the electrodeposition of palladium. The homoleptic LMS of formula [Pd(MeIm)4][Tf2N]2 or [Pd(EtIm)4][Tf2N]2 (MeIm = N-methylimidazole, EtIm = N-ethylimidazole) have higher melting points than the heteroleptic [Pd(MeIm)2(EtIm)2][Tf2N]2, which is proved to be the most promising electrolyte. The deposition reaction in these LMS was found to be irreversible but smooth and dense palladium layers can be deposited that are crack-free up to a thickness of 10 microns. [ABSTRACT FROM AUTHOR]

Ionic liquids containing the hexafluoroacetylacetonate anion are immiscible with water and they exhibit strong metal-complexing ability. [ABSTRACT FROM AUTHOR]

Two series of 1-alkylpyridinium and N-alkyl-N-methylpiperidinium ionic liquids functionalized with a nitrile group at the end of the alkyl chain have been synthesized. Structural modifications include a change of the alkyl spacer length between the nitrile group and the heterocycle of the cationic core, as well as adding methyl or ethyl substituents on different positions of the pyridinium ring. The anions are the bromide and the bis(trifluoromethylsulfonyl)imide ion. All the bis(trifluoromethylsulfonyl)imide salts as well as the bromide salts with a long alkyl spacer were obtained as viscous liquids at room temperature, but some turned out to be supercooled liquids. In addition, pyrrolidinium and piperidinium ionic liquids with two nitrile functions attached to the heterocyclic core have been prepared. The crystal structures of seven pyridinium bis(trifluoromethylsulfonyl)imide salts are reported. Quantum chemical calculations have been performed on model cations and ion pairs with the bis(trifluoromethylsulfonyl)imide anion. A continuum model has been used to take solvation effects into account. These calculations show that the natural partial charge on the nitrogen atom of the nitrile group becomes more negative when the length of the alkyl spacer between the nitrile functional group and the heterocyclic core of the cation is increased. Methyl or methoxy substituents on the pyridinium ring slightly increase the negative charge on the nitrile nitrogen atom due to their electron-donating abilities. The position of the substituent (ortho, meta, or para) has only a very minor effect on the charge of the nitrogen atom. The 15N NMR spectra of the bis(trifluoromethylsulfonyl)imide ionic liquids were recorded with the nitrogen-15 nucleus at its natural abundance. The chemical shift of the 15N nucleus of the nitrile nitrogen atom could be correlated with the calculated negative partial charge on the nitrogen atom. [ABSTRACT FROM AUTHOR]

Electrolytes consisting of sodium bis(fluorosulfonyl)imide (NaFSI) dissolved in glymes (monoglyme, diglyme, and triglyme) were characterized by FT-Raman spectroscopy and 13C, 17O, and 23Na NMR spectroscopy. The glyme:NaFSI molar ratio was varied from 50:1 to 1:1, and it was observed that, in the dilute electrolytes, the sodium salt is completely dissociated into solvent separated ion pairs (SSIPs). However, contact ion pairs (CIPs) and aggregates (AGGs) become the predominant species in more concentrated solutions. Some of the electrolytes with the highest concentrations can be classified as solvate ionic liquids (SILs), where all of the solvent molecules are coordinated to sodium cations. Therefore, these electrolytes are fundamentally different from more dilute electrolytes which are typically used in commercially available secondary batteries. The melting point or glass transition temperature, dynamic viscosity, density, sodium concentration, and ionic conductivity of these solvate ionic liquids are reported as well as the crystal structures of [Na(G3)][FSI] and [Na(G3)2][FSI]. Galvanostatic cycling experiments were performed in coin-type cells with a Na2/3[Mn0.55Ni0.30Co0.15]O2 cathode to study the influence of these electrolytes on the electrochemical stability and charge/discharge behavior. [ABSTRACT FROM AUTHOR]

A deep-eutectic solvent with the properties of an ionic liquid is formed when choline chloride is mixed with copper(II) chloride dihydrate in a 1:2 molar ratio. EXAFS and UV-vis-near-IR optical absorption spectroscopy have been used to compare the coordination sphere of the cupric ion in this ionic liquid with that of the cupric ion in solutions of 0.1 M of CuCl2·2H2O in solvents with varying molar ratios of choline chloride and water. The EXAFS data show that species with three chloride ions and one water molecule coordinated to the cupric ion as well as species with two chloride molecules and two water molecules coordinated to the cupric ion are present in the ionic liquid. On the other hand, a fully hydrated copper(II) ion is formed in an aqueous solution free of choline chloride, and the tetrachlorocuprate(II) complex forms in aqueous choline chloride solutions with more than 50 wt % of choline chloride. In solutions with between 0 and 50 wt % of choline chloride, mixed chloro-aquo complexes occur. Upon standing at room temperature, crystals of CuCl2·2H2O and of Cu(choline)Cl3 formed in the ionic liquid. Cu(choline)Cl3 is the first example of a choline cation coordinating to a transition-metal ion. Crystals of [choline]3[CuCl4][Cl] and of [choline]4[Cu4Cl10O] were also synthesized from molecular or ionic liquid solvents, and their crystal structures were determined. [ABSTRACT FROM AUTHOR]

Uranium(Vl) oxide has been dissolved in three different ionic liquids functionalized with a carboxyl group: betainium bis[(trifluoromethyl)sulfonyl]imide, 1 -(carboxymethyl)-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, and N-(carbosymethyl)-N-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide. The dissolution process results in the formation of uranyl complexes with zwitterionic carboxylate ligands and bis[(trifluoromethyl)sulfonyl]imide (bistriflimide) counterions, An X-ray diffraction study on single crystals of the uranyl complexes revealed that the crystal structure strongly depends on the cationic core appended to the carboxylate groups. The betainium ionic liquid gives a dimeric uranyl complex, the imidazolium ionic liquid a monomeric complex, and the pyrrolidinium ionic liquid a one-dimensional polymeric uranyl complex. Extended X-ray absorption fine structure measurements have been performed on the betainium uranyl complex. The absorption and luminescence spectra of the uranyl betainium complex have been studied in the solid state and dissolved in water, in acetonitrile, and in the ionic liquid betainium bistriflimide, The carboxylate groups remain coordinated to uranyl in acetonitrile and in betainium bistriflimide but not in water. [ABSTRACT FROM AUTHOR]

New ionic liquid crystals (including ionic metallomesogens) based on the pyrrolidinium core are presented. N-Methylpyrrolidine was quaternized with different mesogenic groups connected to a flexible, ω-bromosubstituted alkyl spacer. The length of the flexible alkyl spacer between the cationic head group and the rigid mesogenic group was varied. The substituted pyrrolidinium cations were combined with bromide, bis(trifluoromethylsulfonyl)imide, tetrakis(2-thenoyltrifluoroacetonato)europate(III), and tetrabromouranyl anions. The influence of the type of mesogenic unit, the lengths of the flexible spacer and terminal alkyl chain, the size of the mesogenic group, and the type of anion on the thermotropic mesomorphic behavior was investigated. Furthermore, the phase behavior was thoroughly compared with the previously reported mesomorphism of N-alkyl-N-methylpyrrolidinium salts. Low-ordered smectic A phases of the de Vries type, smectic C phases, higher-ordered smectic F/I phases, as well as crystal smectic phases (E and G, J, H, or K) were observed and investigated by polarizing optical microscopy, differential scanning calorimetry, and powder X-ray diffraction. [ABSTRACT FROM AUTHOR]

Abstract: The complex formed by the reaction of the uranyl ion, UO2 2+, with bromide ions in the ionic liquids 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][Tf2N]) and methyl-tributylammonium bis(trifluoromethylsulfonyl)imide ([MeBu3N][Tf2N]) has been investigated by UV–Vis and U LIII-edge EXAFS spectroscopy and compared to the crystal structure of [Bmim]2[UO2Br4]. The solid state reveals a classical tetragonal bipyramid geometry for [UO2Br4]2− with hydrogen bonds between the Bmim+ and the coordinated bromides. The UV–Vis spectroscopy reveals the quantitative formation of [UO2Br4]2− when a stoichiometric amount of bromide ions is added to UO2(CF3SO3)2 in both Tf2N-based ionic liquids. The absorption spectrum also suggests a D4h symmetry for [UO2Br4]2− in ionic liquids, as previously observed for the [UO2Cl4]2− congener. EXAFS analysis supports this conclusion and demonstrates that the [UO2Br4]2− coordination polyhedron is maintained in the ionic liquids without any coordinating solvent or water molecules. The mean U–O and U–Br distances in the solutions, determined by EXAFS, are, respectively, 1.766(2) and 2.821(2)Å in [Bmim][Tf2N], and, respectively, 1.768(2) and 2.827(2)Å, in [MeBu3N][Tf2N]. Similar results are obtained in both ionic liquids indicating no significant influence of the ionic liquid cation either on the complexation reaction or on the structure of the uranyl species. [Copyright &y& Elsevier]

Highly luminescent anionic samarium(lll) 3-diketonate and dipicolinate complexes were dissolved in the imidazolium ionic liquid 1-hexyl-3-methylimidazolium bis(tnfluoromethylsulfonyl)imide, [C6mim]fTf2N]. The solubility of the complexes in the ionic liquid was ensured by a careful choice of the countercation of the samarium(lll) complex. The samarium(lll) complexes that were considered are [C[sub6]mim][Sm(tta)[sub4]], where tta is 2-thenoyltrifluoroacetonate; [C[sub6]mim][Sm(nta)[sub4]], where nta is 2-naphthoyltrifluoroacetonate; [C[sub6]mim][Sm(hfa)[sub4]], where hfa is hexafluoroacetylacetonate; and [choline][sub3]- [Sm(dpa)[sub3]), where dpa is pyridine-2,6-dicarboxylate (dipicolinate) and [choline][sup+] is (2-hydroxyethyl)trimethyl ammonium, The crystal structures of the tetrakis samarium(llI) β-diketonate complexes revealed a distorted square antiprismatic coordination for the samarium(lll) ion in all three cases. Luminescence spectra were recorded for the samarium(lll) complexes dissolved in the imidazolium ionic liquid as well as in a conventional solvent, that is, acetonitrile or water for the β-diketonate and dipicolinate complexes, respectively. These expenments demonstrate that [C[sub6]mim][Tf[sub2]N] is a suitable spectroscopic solvent for studying samarium(lll) luminescence. High-luminescence quantum yields were observed for the samarium(lll) β-diketonate complexes in solution. [ABSTRACT FROM AUTHOR]

Uranyl complexes dissolved in room-temperature ionic liquids have diagnostic absorption and emission spectra which reflect the molecular symmetry and geometry. In particular, the characteristic vibrational fine structure of the absorption spectra allows identification of the molecular symmetry of a uranyl complex. The concept of speciation of uranylcomplexes is illustrated for the hydrated uranyl ion, the tetrachloro complex [UO2Cl4]2-, the trinitrato complex [UO2(NO3)3], the triacetato complex [UO2(CH3COO)3]-, and the crown ether complex [UO2(18-crown- 6)]2+ in imidazolium and pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids. The competition between 18-crown-6 and small inorganic ligands for coordination to the uranyl ion was investigated. The crystal structures of the hydrolysis product [(UO2)2(μ2-OH)2(H2O)6] [UO2Br4](18-crown-6)4 and imidazolium salt [C6mim]2[UO2Br4] are described. [ABSTRACT FROM AUTHOR]