Liquid Systems Based on Tetra(n-butyl)phosphonium Acetate for the Non-dissolving Pretreatment of a Microcrystalline Cellulose (Avicel PH-101).

A non-dissolving pretreatment consisting in the direct contact of cellulose and the ionic liquid tetra(n-butyl)phosphonium acetate, or its fluid mixtures with other phosphonium ionic liquids or with molecular liquids such as ethanol or DMSO, causes a reduction in the crystallinity of the popular microcrystalline cellulose-type Avicel PH-101 under mild conditions. At the same time, the degree of polymerization and the thermal stability of the pretreated Avicel remain essentially unaltered with respect to the untreated Avicel. The diminution of the crystallinity has been related to the increase of the reactivity of the pretreated Avicel samples via analysis of the kinetics of their enzymatic hydrolysis. For selected samples, this improved reactivity has been confirmed through their effective carboxymethylation under a simplified and milder reaction procedure.

Phosphonium chloromercurate room temperature ionic liquids of variable composition.

The system trihexyl(tetradecyl)phosphonium ([P66614]Cl)/mercury chloride (HgCl2) has been investigated by varying the stoichiometric ratios from 4:1 to 1:2 (25, 50, 75, 100, 150, and 200 mol % HgCl2). All investigated compositions turn out to give rise to ionic liquids (ILs) at room temperature. The prepared ionic liquids offer the possibility to study the structurally and compositionally versatile chloromercurates in a liquid state at low temperatures in the absence of solvents. [P66614]2[HgCl4] is a simple IL with one discrete type of anion, while [P66614]{HgCl3} (with {} indicating a polynuclear arrangement) is an ionic liquid with a variety of polyanionic species, with [Hg2Cl6](2-) apparently being the predominant building block. [P66614]2[Hg3Cl8] and [P66614][Hg2Cl5] appear to be ILs at ambient conditions but lose HgCl2 when heated in a vacuum. For the liquids with the compositions 4:1 and 4:3, more than two discrete ions can be evidenced, namely, [P66614](+), [HgCl4](2-), and Cl(-) and [P66614](+), [HgCl4](2-), and the polynuclear {HgCl3}(-), respectively. The different stoichiometric compositions were characterized by (199)Hg NMR, Raman- and UV-vis spectroscopy, and cyclic voltammetry, among other techniques, and their densities and viscosities were determined. The [P66614]Cl/HgCl2 system shows similarities to the well-known chloroaluminate ILs (e.g., decrease in viscosity with increasing metal content after addition of more than 0.5 mol of HgCl2/mol [P66614]Cl, increasing density with increasing metal content, and the likely formation of polynuclear/polymeric/polyanionic species) but offer the advantage that they are air and water stable.

Mercuric ionic liquids: [C(n)mim][HgX3], where n = 3, 4 and X = Cl, Br.

A series of mercury(II) ionic liquids, [C(n)mim][HgX(3)], where [C(n)mim] = n-alkyl-3-methylimidazolium with n = 3, 4 and X = Cl, Br, have been synthesized following two different synthetic approaches, and structurally characterized by means of single-crystal X-ray structure analysis ([C(3)mim][HgCl(3)] (1), Cc (No. 9), Z = 4, a = 16.831(4) Å, b = 10.7496(15) Å, c = 7.4661(14) Å, ß = 105.97(2)°, V = 1298.7(4) Å(3) at 298 K; [C(4)mim][HgCl(3)] (2), Cc (No. 9), Z = 4, a = 17.3178(28) Å, b = 10.7410(15) Å, c = 7.4706(14) Å, ß = 105.590(13)°, V = 1338.5(4) Å(3) at 170 K; [C(3)mim][HgBr(3)] (3), P2(1)/c (No. 14), Z = 4, a = 10.2041(10) Å, b = 10.7332(13) Å, c = 14.5796(16) Å, ß = 122.47(2)°, V = 1347.2(3) Å(3) at 170 K; [C(4)mim][HgBr(3)] (4), Cc (No. 9), Z = 4, a = 17.093(3) Å, b = 11.0498(14) Å, c = 7.8656(12) Å, ß = 106.953(13)°, V = 1421.1(4) Å(3) at 170 K). Compounds 1, 2, and 4 are isostructural and are characterized by strongly elongated trigonal [HgX(5)] bipyramids, which are connected via common edges in chains. In contrast, 3 contains [Hg(2)Br(6)] units formed by two edge-sharing tetrahedra. With melting points of 69.3 °C (1), 93.9 °C (2), 39.5 °C (3), and 58.3 °C (4), all compounds qualify as ionic liquids. 1, 2, and 4 solidify upon fast cooling as glasses, whereas 3 crystallizes. Cyclic voltammetry shows two separate, quasi-reversible redox processes, which can be associated with the 2Hg(2+)/Hg(2)(2+) and Hg(2)(2+)/2Hg redox couples.

Ionic liquid-based routes to conversion or reuse of recycled ammonium perchlorate.

New, potentially green, and efficient synthetic routes for the remediation and/or re-use of perchlorate-based energetic materials have been developed. Four simple organic imidazolium- and phosphonium-based perchlorate salts/ionic liquids have been synthesized by simple, inexpensive, and nonhazardous methods, using ammonium perchlorate as the perchlorate source. By appropriate choice of the cation, perchlorate can be incorporated into an ionic liquid which serves as its own electrolyte for the electrochemical reduction of the perchlorate anion, allowing for the regeneration of the chloride-based parent ionic liquid. The electrochemical degradation of the hazardous perchlorate ion and its conversion to harmless chloride during electrolysis was studied using IR and (35)Cl NMR spectroscopies.

Sensor technologies based on a cellulose supported platform.

A simple approach to sensor development based on encapsulating a probe molecule in a cellulose support followed by regeneration from an ionic liquid solution is demonstrated here by the codissolution of cellulose and 1-(2-pyridylazo)-2-naphthol in 1-butyl-3-methylimidazolium chloride followed by regeneration with water to form strips which exhibit a proportionate (1 : 1) response to Hg(II) in aqueous solution.

New, highly acidic ionic liquid systems and their application in the carbonylation of toluene.

Based on the surprisingly high solubility of AlCl3 in ionic liquids of type [cation][(CF3SO2)2N], a new class of highly acidic, ionic systems has been developed. First tests in toluene carbonylation revealed high potential of these new acidic ionic liquids as catalyst for arene functionaliziation reactions.

Use of polyoxometalate catalysts in ionic liquids to enhance the dissolution and delignification of woody biomass.

A well-known polyoxometalate, [PV2Mo10O40]5⁻, in both acidic (acidic POM, H5[PV2Mo10O40]) and ionic liquid-compatible form ([C2mim]POM, [1-ethyl-3-methylimidazolium]4H[PV2Mo10O40]), has been studied as a catalyst for the dissolution and delignification of wood in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C(2) mim]OAc). Differences were observed with variables such as the form of POM, POM loading, and reaction conditions. Generally, the addition of POM leads to a faster dissolution, a lower lignin content in the recovered cellulose-rich materials (isolated pulp), and a lower isolated yield of lignin due to its oxidation. Acidic POM decreases the lignin content of the pulp without compromising the yield of the pulp. [C2mim]POM in the IL facilitates greater delignification (lower lignin content in pulp) than the IL with acidic POM; however, the overall pulp yield is also lower indicating some degradation of the carbohydrates. The POM can be recovered with [C2mim]OAc after evaporation of the reconstitution solvent (e.g., acetone/water) and can be reused, albeit with some loss of POM and loss of POM activity under the current conditions.

On the dissolution of non-metallic solid elements (sulfur, selenium, tellurium and phosphorus) in ionic liquids.

Ionic liquids are shown to be good solvents for elemental sulfur, selenium, phosphorus and tellurium, and can be designed to maximise the solubility of these elements. The presence of the [S(3)](*-) radical anion in diluted solutions of sulfur in some ionic liquids has been confirmed, and is the origin of their intense blue colour (cf. lapis lazuli).

The second evolution of ionic liquids: from solvents and separations to advanced materials--energetic examples from the ionic liquid cookbook.

In this Account of the small portion of the recent research in ionic liquids (ILs) by the Rogers Group, we fast forward through the first evolution of IL research, where ILs were studied for their unique set of physical properties and the resulting potential for tunable "green solvents", to the second evolution of ILs, where the tunability of the cation and anion independently offers almost unlimited access to targeted combinations of physical and chemical properties. This approach is demonstrated here with the field of energetic ionic liquids (EILs), which utilizes this design flexibility to find safe synthetic routes to ILs with high energy content and targeted physical properties.