Structural Features and Properties of Metal Complexes in Ionic Liquids: Application in Alkylation Reactions

Metal-containing ionic liquids (ILs) represent a promising sub-class of “charged” liquids which increase the tunability of ILs combining the properties of common organic salts with magnetic, photophysical/optical or catalytic properties of the incorporated metal salts. In ILs lacking of coordinating groups on cation dissolution of metal salts is generally associated with the coordination of the metal cation with IL anion(s). Here we report on the anionic speciation of metals in ILs having either highly or poorly coordinating anions and we discuss some peculiar properties of these systems in the light of their structural features

Pilot-scale study on masking agents for titanium tanning

The many advantages offered by chrome tanning justify its widespread use for production of almost all types of leather. However, the traditional chromium(III) tanning process is constantly under threat from the pressure of legislation, and ever-tightening restrictions require to minimize chromium-containing effluents discharge and chromium-containing wastes production. Recently, the manufacture and use of chromium(III) free tanning agents compounds have been studied intensively. Among these, Titanium (IV)-based salts is one of the most promising substitutes. In this study, the use of titanyl sulfate as tanning agent for the production of high-quality bovine upper leather was investigated. In order to optimize the titanium tanning performances, a comparative evaluation, on pilot-scale, of citrate and lactate ions as masking agents was performed. The developed process has been validated through various analyses of the obtained crust leathers such as shrinkage temperature, scanning electron microscopy, and physical testing. The final leather obtained with the innovative method shows similar properties to those of the conventional tanned leather in terms of technical and mechanical properties

Dissolution of metal salts in bis(trifluoromethylsulfonyl)imide-based ionic liquids: Studying the affinity of metal cations toward a "weakly coordinating" anion

Despite the weakly coordinating ability of the bis(trifluoromethylsulfonyl)imide anion ([Tf2N]-) the corresponding ionic liquids (ILs) are able to dissolve relevant amounts of metal salts having the same anion, M[Tf2N]x. To better understand the metal dissolution process we evaluated the interaction ability of a set of metal cations (Y(III), Al(III), Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Li(I), and Na(I)) toward the [Tf2N]- anion measuring the relative aptitude to give the corresponding anionic monocharged complex, [M(Tf2N)x+1]- using the ESI-MS technique. UV-vis and NMR measurements were carried out to verify the consistence between the liquid and the gas phase. Density functional theory calculations have been used to identify the metal-containing species and determine their relative stability. An interesting correlation between interaction ability and chemical properties (Lewis acidity) was found

Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids

New thiol-functionalized carboxylate ionic liquids (ILs), varying both for the cation and for the anion structures, have been prepared as new potential redox switching systems by reacting either 3-mercapto propionic acid (3-MPA) or N-acetyl-cysteine (NAC) with commercially available methyl carbonate ILs. Dierent ratios of thiol/disulfide ILs were obtained depending both on the acid employed in the neutralization reaction and on the reaction conditions used. Surprisingly, the imidazolium ILs displayed limited thermal stability which resulted in the formation of an imidazole 2-thione and a new sulfide ionic liquid. Conversely, the formation of the imidazole 2-thione was not observed when phosphonium disulfide ILs were heated, thus confirming the involvement of the imidazolium ring in an unexpected side reaction. An insight into the mechanism of the decomposition has been provided by means of DFT calculations

A general environmentally friendly access to long chain fatty acid ionic liquids (LCFA-ILs)

The development of bio-based ionic liquids (ILs) has attracted a great deal of interest in recent years. The so called long chain fatty acid ionic liquids (LCFA-ILs) represent a bio-based subfamily of hydrophobic ionic liquids. Here, a new preparation of the three major classes of LCFA-ILs (phosphonium, ammonium, imidazolium) is presented with the aim to overcome previous environmental synthetic issues. The undeniable interesting properties and potential applications of the LCFA-ILs often led to the underestimation of the drawbacks related to their synthetic pathways. Pure LCFA-ILs as well as cheaper mixture of LCFA-ILs have been obtained in a single step, in almost quantitative yields, and without production of waste water. The rheological and thermal stability properties of the prepared ILs have been analyzed

A Specific Interaction between Ionic Liquids' Cations and Reichardt's Dye

Solvatochromic probes are often used to understand solvation environments at the molecular scale. In the case of ionic liquids constituted by an anion and a cation, which are designed and paired in order to obtain a low melting point and other desirable physicochemical properties, these two indivisible components can interact in a very different way with the probe. This is the case with one of the most common probes: Reichardt's Dye. In the cases where the positive charge of the cation is delocalized on an aromatic ring such as imidazolium, the antibonding orbitals of the positively charged aromatic system are very similar in nature and energy to the LUMO of Reichardt's Dye. This leads to an interesting, specific cation-probe interaction that can be used to elucidate the nature of the ionic liquids' cations. Parallel computational and experimental investigations have been conducted to elucidate the nature of this interaction with respect to the molecular structure of the cation

Chiral ionic liquid assisted synthesis of some metal oxides

A chiral ionic liquid with a natural alcohol based chain was used as a tailoring agent for the synthesis of simple and cost effective materials such as ZnO, CuO, CuO-ZnO with peculiar morphology. The morphology and chemical composition of the microstructures were investigated by bright-field and scanning transmission microscopy (BF-TEM and STEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and UV-VIS spectroscopy. Furthermore, the photocatalytic activity of ZnO, CuO and ZnO-CuO nanostructures was quantified for methylene blue (MB) dye. CuO needles had the lowest photocatalytic activity (23.8% in 40 min). Due to their peculiar forms, ZnO (flower like shape) and ZnO/CuO (leaf like shape where ZnO nanoparticles were deposited) had the highest photocatalytic activity in 40 min (93.6% for ZnO nanoparticles and 95% for ZnO-CuO nanostructures)

Expanding the Chemical Space of Benzimidazole Dicationic Ionic Liquids

Benzimidazole dicationic ionic liquids (BDILs) have not yet been widely explored in spite of their potential. Therefore, two structurally related families of BDILs, paired with either bromide or bistriflimide anions and bearing alkyl spacers ranging from C3 to C6, have been prepared. Their thermal properties have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), while their electrical properties have been assessed by cyclic voltammetry (CV). TG analysis confirmed the higher stability of the bistriflimide BDILs over the bromide BDILs, with minor variation within the two families. Conversely, DSC and CV allowed for ascertaining the role played by the spacer length. In particular, the thermal behavior changed dramatically among the members of the bistriflimide family, and all three possible thermal behavior types of ILs were observed. Furthermore, cyclic voltammetry showed different electrochemical window (C3(C1BenzIm)2/2Tf2N < C4(C1BenzIm)2/2Tf2N, C5(C1BenzIm)2/2Tf2N < C6(C1BenzIm)2/2Tf2N) as well as a reduction peak potential, shape, and intensity as a function of the spacer length. The results obtained highlight the benefit of accessing a more structurally diverse pool of compounds offered by dicationic ILs when compared to the parent monocationic ILs. In particular, gains are to be found in the ease of fine-tuning their properties, which translates in facilitating further investigations toward BDILs as designer solvents and catalysts

Chiral ionic liquids supported on natural sporopollenin microcapsules

Supported chiral ionic liquids (SILs) were prepared choosing the starting material for the ionic liquid part from the enantiopure stock of the chiral pool (monoterpenoids and an amino acid) and the sporopollenin as an environmentally friendly support. Sporopollenins are microcapsules with naturally well-defined sizes and shapes that can be obtained from pollen grains after removal of the internal cytoplasm and the second shell layer. As thermally stable organic biocompatible structures, sporopollenins have attracted increasing interest in recent years for several applications. Herein, bio-based ILs were anchored onto the surface of sporopollenins obtained from the pollen of Populus deltoides, selected as a model pollen grain. These new structures, which present an external positively charged shell, were characterized by physico-chemical techniques (ATR-FTIR, TGA, SEM, EDX, and solid-state 13C NMR). A metathesis reaction was also performed on selected bio-based IL modified sporopollenins, demonstrating the possibility to switch the surface properties by exploiting well-known IL chemistry

Alkylation of methyl linoleate with propene in ionic liquids in the presence of metal salts

Vegetable oils and fatty acid esters are suitable precursor molecules for the production of a variety of bio-based products and materials, such as paints and coatings, plastics, soaps, lubricants, cosmetics, pharmaceuticals, printing inks, surfactants, and biofuels. Here, we report the possibility of using Lewis acidic ionic liquids (ILs) to obtain polyunsaturated ester dimerization-oligomerization and/or, in the presence of another terminal alkene (propene), co-polymerization. In particular, we have tested the Lewis acidic mixtures arising from the addition of a proper amount of GaCl3 (X > 0.5) to two chloride-based (1-butyl-3-methylimidazolium chloride, [bmim]Cl, and 1-butylisoquinolium chloride, [BuIsoq]Cl) or by dissolution of a smaller amount of Al(Tf2N)3 (X = 0.1) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][Tf2N]. On the basis of product distribution studies, [bmim][Tf2N]/Al(Tf2N)3 appears the most suitable medium in which methyl linoleate alkylation with propene can compete with methyl linoleate or propene oligomerization