Heavy Elements in Ionic Liquids

TiCl4 Dissolved in Ionic Liquid Mixtures from ab Initio Molecular Dynamics Simulations

To gain a deeper understanding of the TiCl4 solvation effects in multi-component ionic liquids, we performed ab initio molecular dynamics simulations of 1-butyl-3-methylimidazolium [C4C1Im]+, tetrafluoroborate [BF4]−, chloride [Cl]− both with and without water and titanium tetrachloride TiCl4. Complex interactions between cations and anions are observed in all investigated systems. By further addition of water and TiCl4 this complex interaction network is extended. Observations of the radial distribution functions and number integrals show that water and TiCl4 not only compete with each other to interact mainly with [Cl]−, which strongly influences the cation-[BF4]− interaction, but also interact with each other, which leads to the fact that in certain systems the cation-anion interaction is enhanced. Further investigations of the Voronoi polyhedra analysis have demonstrated that water has a greater impact on the nanosegregated system than TiCl4 which is also due to the fact of the shear amount of water relative to all other components and its higher mobility compared to TiCl4. Overall, the polar network of the IL mixture collapses by including water and TiCl4. In the case of [Cl]− chloride enters the water continuum, while [BF4]− remains largely unaffected, which deeply affects the interaction of the ionic liquid (IL) network.

Tetrabromidocuprates(II)-Synthesis, Structure and EPR

Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several "onium" cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g‖ and g⊥) of the tensors could be determined and information on the structural changes in the [CuBr₄](2-) anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids.

Nonstoichiometric, Protic Azolium Azolate Ionic Liquids Provide Unique Environments for N-Donor Coordination Chemistry

Here we demonstrate that neat reactions of amphoteric azoles with more basic azoles give a family of finely tunable, nonstoichiometric liquids which are useful for N-donor coordination chemistry. Reacting 4,5-dicyanoimidazole (4,5-DCNIm) with 1-methylimidazole (1-mim) gives new compounds with composition-dependent speciation. Two crystalline compounds, a 1:1 protic salt, [H(1-mim)][4,5-DCNIm], and a 1:2 salt co-crystal, [H(1-mim)][4,5-DCNIm]⋅4,5-DCNIm, were isolated and structurally characterized, while differential scanning calorimetry revealed both suppression of crystallization and the presence of neutral and anionic species in the melt. Reactions of Cu(NO3 )2 ⋅2.5 H2 O, CuO, and ZnO with the neat 2:1 1-mim/4,5-DCNIm melt resulted in the isolation of entirely N-donor ligated complexes of the formula M(4,5-DCNIm)2 (1-mim)4 (M=Cu, Zn).

Isolation of Uranyl Dicyanamide Complexes from N-Donor Ionic Liquids

An ionic liquid (IL) approach for soft-donor f-element chemistry has been demonstrated by the isolation of several new uranyl dicyanamide complexes through reactions of UO2(NO3)2·6H2O with dicyanamide ([N(CN)2](-))-containing ILs. The [N(CN)2](-) ions are able to rapidly substitute uranium's O-donor ligands, as evidenced by single-crystal X-ray diffraction studies on two anhydrous adducts of UO2(NO3)2 with [N(CN)2](-) ILs as well as by IR and NMR spectroscopic studies on solutions of UO2(NO3)2 in these ILs. By contrast, the slow reaction of UO2(OAc)2·2H2O with a nitrile-functionalized imidazolium dicyanamide IL in solvent and the reaction of UO2(NO3)2·6H2O with NaN(CN)2 at elevated temperature resulted in irreversible hydrolysis. The reaction of UO2SO4 with [N(CN)2](-) ions in an acidified aqueous solution resulted in the crystallization of a [UO2](2+) complex with biuret, a N(CN)2](-) hydrolysis product. [N(CN)2](-) ions in the form of ILs react rapidly with [UO2](2+) at room temperature, allowing ligand substitution with [N(CN)2](-) to out-compete the slower hydrolysis reaction, enabling the isolation of uranyl dicyanamide complexes and challenging assumptions regarding the affinity of uranium for O-donors.

Ionic liquid-assisted formation of cellulose/calcium phosphate hybrid materials

Cellulose/calcium phosphate hybrid materials were synthesized via an ionic liquid-assisted route. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis/differential thermal analysis show that, depending on the reaction conditions, cellulose/hydroxyapatite, cellulose/chlorapatite, or cellulose/monetite composites form. Preliminary studies with MC3T3-E1 pre-osteoblasts show that the cells proliferate on the hybrid materials suggesting that the ionic liquid-based process yields materials that are potentially useful as scaffolds for regenerative therapies.

A new general synthetic strategy for phase-pure complex functional materials

The ability of ionic liquids to solvate inorganic salts completely has to date never been employed in the synthesis of complex inorganic materials. Here, we demonstrate that complex functional oxides, even those traditionally considered extremely difficult to synthesize in bulk, such as quinternary superconductors, are produced with no impurity phases and on timescales that are much shorter than other synthetic techniques.

Tetrachloridocuprates(II)-synthesis and electron paramagnetic resonance (EPR) spectroscopy

Ionic liquids (ILs) on the basis of metal containing anions and/or cations are of interest for a variety of technical applications e.g., synthesis of particles, magnetic or thermochromic materials. We present the synthesis and the results of electron paramagnetic resonance (EPR) spectroscopic analyses of a series of some new potential ionic liquids based on tetrachloridocuprates(II), [CuCl₄]²⁻, with different sterically demanding cations: hexadecyltrimethylammonium 1, tetradecyltrimethylammonium 2, tetrabutylammonium 3 and benzyltriethylammonium 4. The cations in the new compounds were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy. The EPR hyperfine structure was not resolved. This is due to the exchange broadening, resulting from still incomplete separation of the paramagnetic Cu(II) centers. Nevertheless, the principal values of the electron Zeemann tensor (g_║ and g_┴) of the complexes could be determined. Even though the solid substances show slightly different colors, the UV/Vis spectra are nearly identical, indicating structural changes of the tetrachloridocuprate moieties between solid state and solution. The complexes have a promising potential e.g., as high temperature ionic liquids, as precursors for the formation of copper chloride particles or as catalytic paramagnetic ionic liquids.

Microwave synthesis and inherent stabilization of metal nanoparticles in 1-methyl-3-(3-carboxyethyl)-imidazolium tetrafluoroborate

The synthesis of Co-NPs and Mn-NPs by microwave-induced decomposition of the metal carbonyls Co(2)(CO)(8) and Mn(2)(CO)(10), respectively, yields smaller and better separated particles in the functionalized IL 1-methyl-3-(3-carboxyethyl)-imidazolium tetrafluoroborate [EmimCO(2)H][BF(4)] (1.6 ± 0.3 nm and 4.3 ± 1.0 nm, respectively) than in the non-functionalized IL 1-n-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF(4)]. The particles are stable in the absence of capping ligands (surfactants) for more than six months although some variation in particle size could be observed by TEM.

Thermomorphic behavior of the ionic liquids [C4mim][FeCl4] and [C12mim][FeCl4]

The iron-containing ionic liquids 1-butyl-3-methylimidazolium tetrachloroferrate(III) [C(4)mim][FeCl(4)] and 1-dodecyl-3-methylimidazolium tetrachloroferrate(III) [C(12)mim][FeCl(4)] exhibit a thermally induced demixing with water (thermomorphism). The phase separation temperature varies with IL weight fraction in water and can be tuned between 100 °C and room temperature. The reversible lower critical solution temperature (LCST) is only observed at IL weight fractions below ca. 35 % in water. UV/Vis, IR, and Raman spectroscopy along with elemental analysis prove that the yellow-brown liquid phase recovered after phase separation is the starting IL [C(4)mim][FeCl(4)] and [C(12)mim][FeCl(4)], respectively. Photometry and ICP-OES show that about 40 % of iron remains in the water phase upon phase separation. Although the process is thus not very efficient at the moment, the current approach is the first example of an LCST behavior of a metal-containing IL and therefore, although still inefficient, a prototype for catalyst removal or metal extraction.