Designing Dimeric Lanthanide(III)-Containing Ionic liquids.

Herein, we report on the preparation of liquid dimeric lanthanide(III)-containing compounds. Starting from the design of dimeric solids, we demonstrate that by tuning of anion and cation structures we can lower the melting points below room temperature, whilst maintaining the dimeric structure. Magnetic measurements could establish the spin-spin interactions of the neighboring lanthanide(III) ions in the liquid state at low temperatures, and matched the interactions of the analogous crystalline solid compounds.

Taming Tris(bipyridine)ruthenium(II) and Its Reactions in Water by Capture/Release with Shape-Switchable Symmetry-Matched Cyclophanes.

Electron/proton transfers in water proceeding from ground/excited states are the elementary reactions of chemistry. These reactions of an iconic class of molecules─polypyridineRu(II)─are now controlled by capturing or releasing three of them with hosts that are shape-switchable. Reversible erection or collapse of the host walls allows such switchability. Some reaction rates are suppressed by factors of up to 120 by inclusive binding of the metal complexes. This puts nanometric coordination chemistry in a box that can be open or shut as necessary. Such second-sphere complexation can allow considerable control to be exerted on photocatalysis, electrocatalysis, and luminescent sensing involving polypyridineRu(II) compounds. The capturing states of hosts are symmetry-matched to guests for selective binding and display submicromolar affinities. A perching complex, which is an intermediate state between capturing and releasing states, is also demonstrated.

Spontaneous Substitutions at Phosphorus Trihalides in Imidazolium Halide Ionic Liquids: Grotthuss Diffusion of Anions?

PX3 compounds (X=Cl, Br, I) in imidazolium halide ionic liquids combine with the anion Z (Z=Cl, Br, I) of the solvent to form [PX3 Z]- complex anions. These anions have a sawhorse shape in which the lone pair of the phosphorus atom fills the third equatorial position of the pseudotrigonal bipyramid. Theoretical results show that this association remains incomplete due to strong hydrogen bonding with the cations of the ionic liquid, which competes with the phosphorus trihalide for interaction with the Z- anion. Temperature-dependent 31 P NMR experiments indicated that the P-Z binding is weaker at higher temperature. Both theory and experiment evidence dynamic exchange of the halide anions at the phosphorus atom, together with continuous switching of the ligands at the phosphorus atom between equatorial and axial positions. Detailed knowledge of the mechanism of the spontaneous exchange of halogen atoms at phosphorus trihalides suggests a way to design novel, highly conducting ionic-liquid mixtures.

Ionothermal syntheses of nano- and microstructured ternary copper-indium-chalcogenides.

Ternary compounds of copper indium selenide nano- and microsized materials were prepared through colloidal synthesis using an indium(III) selenide precursor and copper(I) chloride via a microwave-assisted ionothermal route. The indium(III) selenide precursor used in the reaction was formed in situ from a diphenyl diselenide precursor and chloroindate(III) ionic liquids (ILs), also via a microwave-assisted ionothermal route. The crystal structures of three intermediates, namely, CuCl2(OMe)2(H2O)){Cu(PhSeO2)2}n, [CuCl(Se2Ph2)2]n, and [C8mim]3{Cu(I)Cl2Cu(II)OCl8}n, were determined after formation through a ionothermal procedure utilizing metal-containing imidazolium ILs and a selenium precursor with conventional heating. Herein, we compare the use of microwave irradiation over conventional heating with different ILs on the stoichiometry of the resulting products. The influence of the reaction temperature, reaction time, order of addition of reagents, and variation of ILs, which were characterized using PXRD, SEM, and EDX, on the final products was investigated.

3-Methylpiperidinium ionic liquids.

A wide range of room temperature ionic liquids based on the 3-methylpiperdinium cation core were produced from 3-methylpiperidine, which is a derivative of DYTEK® A amine. First, reaction with 1-bromoalkanes or 1-bromoalkoxyalkanes generated the corresponding tertiary amines (Rmßpip, R = alkyl or alkoxyalkyl); further quaternisation reactions with the appropriate methylating agents yielded the quaternary [Rmmßpip]X salts (X(-) = I(-), [CF3CO2](-) or [OTf](-); Tf = -SO2CF3), and [Rmmßpip][NTf2] were prepared by anion metathesis from the corresponding iodides. All [NTf2](-) salts are liquids at room temperature. [Rmmßpip]X (X(-) = I(-), [CF3CO2](-) or [OTf](-)) are low-melting solids when R = alkyl, but room temperature liquids upon introduction of ether functionalities on R. Neither of the 3-methylpiperdinium ionic liquids showed any signs of crystallisation, even well below 0 °C. Some related non-C-substituted piperidinium and pyrrolidinium analogues were prepared and studied for comparison. Crystal structures of 1-hexyl-1,3-dimethylpiperidinium tetraphenylborate, 1-butyl-3-methylpiperidinium bromide, 1-(2-methoxyethyl)-1-methylpiperidinium chloride and 1-(2-methoxyethyl)-1-methylpyrrolidinium bromide are reported. Extensive structural and physical data are collected and compared to literature data, with special emphasis on the systematic study of the cation ring size and/or asymmetry effects on density, viscosity and ionic conductivity, allowing general trends to be outlined. Cyclic voltammetry shows that 3-methylpiperidinium ionic liquids, similarly to azepanium, piperidinium or pyrrolidinium counterparts, are extremely electrochemically stable; the portfolio of useful alternatives for safe and high-performing electrolytes is thus greatly extended.

Novel chiral ionic liquids: physicochemical properties and investigation of the internal rotameric behaviour in the neat system.

Optically active S-alkyl-N,N'-bis((S)-1-phenylethyl)thiouronium salts, abbreviated as (S)-[C(n)petu]Y (where Y is an anion; n = 1, 2, 3, 4, 6, 8, 10, 12 or 16), have been prepared and studied by a broad spectrum of analyses. This consists of density, viscosity, and conductivity determination, followed by a discussion of relevant correlations. Unusual trends depending on the S-alkyl chain length were documented for (S)-[C(n)petu][NTf2] series (where [NTf2](-) = bis{(trifluoromethyl)sulfonyl}amide), including the viscosity decreasing with increasing chain length, and the conductivity showing a maximum between the S-butyl and the S-hexyl derivative. In addition, a hindered rotamerism of the thiouronium cation in dmso-d6 solution was recognised by (1)H and (13)C NMR techniques. Thorough analysis of NMR spectra confirmed that the main contribution comes from rotation about the partial double C-S bond. For the first time, a neat thiouronium ionic liquid system has been subjected to quantitative analysis of hindered rotamerism by dynamic NMR coalescence studies, with estimated activation energy for rotation of 63.9 ± 0.4 kJ mol(-1). Finally, the application of (S)-[C(n)petu]Y salts as chiral discriminating agents for carboxylates by (1)H NMR spectroscopy was further investigated, demonstrating the influence of the S-alkyl chain length on chiral recognition; (S)-[C2petu][NTf2] ionic liquid with the mandelate anion gave the best results.

Electrical conductivity and glass formation in nitrile-functionalized pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids: chain length and odd-even effects of the alkyl spacer between the pyrrolidinium ring and the nitrile group.

The electrical conductivity of a series of pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids, functionalized with a nitrile (cyano) group at the end of an alkyl chain attached to the cation, was studied in the temperature range between 173 K and 393 K. The glass formation of the ionic liquids is influenced by the length of the alkyl spacer separating the nitrile function from the pyrrolidinium ring. The electrical conductivity and the viscosity do not show a monotonic dependence on the alkyl spacer length, but rather an odd-even effect. An explanation for this behavior is given, including the potential energy landscape picture for the glass transition.

Enantioselective assembly of a ruthenium(II) polypyridyl complex into a double helix.

Evolution can increase the complexity of matter by self-organization into helical architectures, the best example being the DNA double helix. One common aspect, apparently shared by most of these architectures, is the presence of covalent bonds within the helix backbone. Here, we report the unprecedented crystal structures of a metal complex that self-organizes into a continuous double helical structure, assembled by non-covalent building blocks. Built up solely by weak stacking interactions, this alternating tread stairs-like double helical assembly mimics the DNA double helix structure. Starting from a racemic mixture in aqueous solution, the ruthenium(II) polypyridyl complex forms two polymorphic structures of a left-handed double helical assembly of only the Λ-enantiomer. The stacking of the helices is different in both polymorphs: a crossed woodpile structure versus a parallel columnar stacking.

Chlorostannate(II) ionic liquids: speciation, Lewis acidity, and oxidative stability.

The anionic speciation of chlorostannate(II) ionic liquids, prepared by mixing 1-alkyl-3-methylimidazolium chloride and tin(II) chloride in various molar ratios, χ(SnCl2), was investigated in both solid and liquid states. The room temperature ionic liquids were investigated by (119)Sn NMR spectroscopy, X-ray photoelectron spectroscopy, and viscometry. Crystalline samples were studied using Raman spectroscopy, single-crystal X-ray crystallography, and differential scanning calorimetry. Both liquid and solid systems (crystallized from the melt) contained [SnCl(3)](-) in equilibrium with Cl(-) when χ(SnCl(2)) < 0.50, [SnCl(3)](-) in equilibrium with [Sn(2)Cl(5)](-) when χ(SnCl(2)) > 0.50, and only [SnCl(3)](-) when χ(SnCl(2)) = 0.50. Tin(II) chloride was found to precipitate when χ(SnCl(2)) > 0.63. No evidence was detected for the existence of [SnCl(4)](2-) across the entire range of χ(SnCl(2)), although such anions have been reported in the literature for chlorostannate(II) organic salts crystallized from organic solvents. Furthermore, the Lewis acidity of the chlorostannate(II)-based systems, expressed by their Gutmann acceptor number, has been determined as a function of the composition, χ(SnCl(2)), to reveal Lewis acidity for χ(SnCl(2)) > 0.50 samples comparable to the analogous systems based on zinc(II). A change of the Lewis basicity of the anion was estimated using (1)H NMR spectroscopy, by comparison of the measured chemical shifts of the C-2 hydrogen in the imidazolium ring. Finally, compositions containing free chloride anions (χ(SnCl(2)) < 0.50) were found to oxidize slowly in air to form a chlorostannate(IV) ionic liquid containing the [SnCl(6)](2-) anion.

Tuneable-by-design copper oxide nanoparticles in ionic liquid nanofluids.

In this study, copper oxide nanoparticles (CuO-NPs) were synthesised in an ionic liquid, [C2MIm][CnHnCO2], and the respective copper(II) carboxylate precursors. Heating the solution to 120 °C caused a colour change from blue to red, indicating a change in copper salt coordination and nanoparticle formation. Crystallography and UV-Vis spectroscopy were used to monitor the transition upon temperature changes. The particle formation was characterised using TEM and SWAXS analyses. The results showed that different anion chain lengths led to different particle sizes. When using copper(II) acetate precursors, the transformation resulted in CuO(I,II) clusters (<1 nm), depending on the imidazolium-based cation used. However, using a copper(II) octanoate precursor, small CuO-NPs in the range of 10-25 nm were formed, while larger CuO-NPs were obtained using a copper(II) butanoate precursor in the range of 10-61 nm.

Advancing mesoporous carbon synthesis for supercapacitors: a systematic investigation of cross-linking agent effects on pore structure and functionality.

Soft-templating synthesis provides an effective route to prepare ordered mesoporous carbons (MCs) that can be used for supercapacitors. During this process, the cross-linking of carbon precursors is critical to obtain tailored pore structural MCs, thus careful selection of appropriate cross-linking agents is required. Despite the shift from the prevailing cross-linker formaldehyde to its more environmentally friendly alternatives, detailed understanding on the influence of different cross-linking agents on templating synthesis is still lacking. Therefore, it remains challenging to draw a conclusion regarding which cross-linker can effectively enable an ideal cross-linking and a robust templating synthesis of ordered MCs. This work presents a systematic study, by comparing three typical cross-linkers (formaldehyde, glyoxal, and glyoxylic acid), on the pore architecture, surface functionality, and electrochemical performance of resulting MCs. Both the type of cross-linker and its ratio with precursor monomer were found to be crucial for the pore architecture and electrochemical performance of resulting MCs. Glyoxal showed to be a promising cross-linker for easily generating ordered mesopores between 3.3-6.1 nm when the molar ratio between cross-linker and carbon precursor ranged from 1 to 2, whereas glyoxylic acid and formaldehyde induced interrupted or disordered mesopores. When the resulting MCs were used as supercapacitor electrodes, those cross-linked with glyoxal also led to overall higher capacitance in both 6 M KOH aqueous and ionic liquid [N2220][NTf2]/acetonitrile electrolytes thanks to the dominance of ordered mesopore channels, especially MC prepared at glyoxal/precursor molar ratio of 1.5. These findings on the effect of cross-linking on templating synthesis can be used to guide the customisation of MCs for supercapacitors and other applications by smartly choosing a suitable cross-linking agent and its ratio with the precursor.

Ionic liquid-assisted synthesis of mesoporous polymers and carbon materials: the self-assembly mechanism.

Soft-templating synthesis has been widely employed to fabricate ordered mesoporous polymer and carbon materials with effectively tuneable pore sizes. However, the commonly used templating agents, block copolymers, are normally decomposed during the process, thus are barely recyclable; this increases the costs and hampers the scale-up feasibility. Therefore, it becomes imperative to seek promising alternatives; amphiphilic ionic liquids (ILs) are excellent candidates due to their good recyclability. This study explored the templating behaviour of IL templates for preparing mesoporous polymers and carbons. In details, the self-assembly of ternary systems (comprising of IL templates, precursors and solvent) were investigated by a combination of coarse-grained molecular dynamics (CGMD) simulations, density function theory (DFT) calculations and experimental techniques. The results indicate that the morphologies of IL templates are tuneable not only by the adjustment of water content in the mixture but also by the selection of suitable precursors. Material precursors containing increasing numbers of hydroxyl moieties also induce various precursor-template spatial correlations, resulting in different topological structures of nanomaterials. This work presents a fundamental investigation into the mechanisms of templating synthesis with amphiphilic ILs as recyclable templates and gives insight into the effective design of coveted carbon nanomaterials for targeted applications.

Validation of speciation techniques: a study of chlorozincate(II) ionic liquids.

The speciation of chlorozincate(II) ionic liquids, prepared by mixing 1-octyl-3-methylimidazolium chloride, [C(8)mim]Cl, and zinc(II) chloride in various molar ratios, χ(ZnCl(2)), was investigated using Raman spectroscopy and differential scanning calorimetry; the Gutmann acceptor number, which is a quantitative measure of Lewis acidity, was also determined as a function of the composition. These results were combined with literature data to define the anionic speciation; in the neat liquid phase, the existence of Cl(-), [ZnCl(4)](2-), [Zn(2)Cl(6)](2-), [Zn(3)Cl(8)](2-), and [Zn(4)Cl(10)](2-) anions was confirmed. From two chlorozincate(II) ionic liquids with [C(2)mim](+) cations (χ(ZnCl(2)) = 0.33 and χ(ZnCl(2)) = 0.50), crystals have been obtained, revealing the structures of [C(2)mim](2)[ZnCl(4)] and [C(2)mim](2)[Zn(2)Cl(6)] forming three-dimensional hydrogen-bond networks. The compound [C(2)mim](2){Zn(4)Cl(10)} was crystallized from the χ(ZnCl(2)) = 0.75 composition, showing an open-framework structure, with the first example of zinc in a trigonal-bipyramidal chloride coordination. Reinvestigation of the electrospray ionization mass spectrometry of these systems demonstrated that it is an unreliable technique to study liquid-phase speciation.

Spectroscopic Signatures of Hydrogen-Bonding Motifs in Protonic Ionic Liquid Systems: Insights from Diethylammonium Nitrate in the Solid State.

Diethylammonium nitrate, [N0 0 2 2][NO3], and its perdeuterated analogue, [N D D 2 2] [NO3], were structurally characterized and studied by infrared, Raman, and inelastic neutron scattering (INS) spectroscopy. Using these experimental data along with state-of-the-art computational materials modeling, we report unambiguous spectroscopic signatures of hydrogen-bonding interactions between the two counterions. An exhaustive assignment of the spectral features observed with each technique has been provided, and a number of distinct modes related to NH···O dynamics have been identified. We put a particular emphasis on a detailed interpretation of the high-resolution, broadband INS experiments. In particular, the INS data highlight the importance of conformational degrees of freedom within the alkyl chains, a ubiquitous feature of ionic liquid (IL) systems. These findings also enable an in-depth physicochemical understanding of protonic IL systems, a first and necessary step to the tailoring of hydrogen-bonding networks in this important class of materials.

Cobalt(II) complexes of nitrile-functionalized ionic liquids.

A series of nitrile-functionalized ionic liquids were found to exhibit temperature-dependent miscibility (thermomorphism) with the lower alcohols. Their coordinating abilities toward cobalt(II) ions were investigated through the dissolution process of cobalt(II) bis(trifluoromethylsulfonyl)imide and were found to depend on the donor abilities of the nitrile group. The crystal structures of the cobalt(II) solvates [Co(C(1)C(1CN)Pyr)(2)(Tf(2)N)(4)] and [Co(C(1)C(2CN)Pyr)(6)][Tf(2)N](8), which were isolated from ionic-liquid solutions, gave an insight into the coordination chemistry of functionalized ionic liquids. Smooth layers of cobalt metal could be obtained by electrodeposition of the cobalt-containing ionic liquids.

Uranyl complexes of carboxyl-functionalized ionic liquids.

Uranium(VI) 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-(carboxymethyl)-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.

Ionic liquid as plasticizer for europium(III)-doped luminescent poly(methyl methacrylate) films.

Flexible luminescent polymer films were obtained by doping europium(III) complexes in blends of poly(methyl methacrylate) (PMMA) and the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(6)mim][Tf(2)N]. Different europium(III) complexes have been incorporated in the polymer/ionic liquid matrix: [C(6)mim][Eu(nta)(4)], [C(6)mim][Eu(tta)(4)], [Eu(tta)(3)(phen)] and [choline](3)[Eu(dpa)(3)], where nta is 2-naphthoyltrifluoroacetonate, tta is 2-thenoyltrifluoroacetonate, phen is 1,10-phenanthroline, dpa is 2,6-pyridinedicarboxylate (dipicolinate) and choline is the 2-hydroxyethyltrimethyl ammonium cation. Bright red photoluminescence was observed for all the films upon irradiation with ultraviolet radiation. The luminescent films have been investigated by high-resolution steady-state luminescence spectroscopy and by time-resolved measurements. The polymer films doped with beta-diketonate complexes are characterized by a very intense (5)D(0)-->(7)F(2) transition (up to 15 times more intense than the (5)D(0)-->(7)F(1)) transition, whereas a marked feature of the PMMA films doped with [choline](3)[Eu(dpa)(3)] is the long lifetime of the (5)D(0) excited state (1.8 ms).

Influence of the anion on the electrical conductivity and glass formation of 1-butyl-3-methylimidazolium ionic liquids.

Six ionic liquids based on the 1-butyl-3-methylimidazolium cation have been studied. As anions Cl(-), Br(-), I(-), [NCS](-), [N(CN)(2)](-), and [BF(4)](-) were selected. The electrical conductivities were determined between 173 and 393 K based on impedance measurements in the frequency range from 0.1 to 10(7) Hz. The electrical conductivity increases, whereas the glass transition temperature, the fragility, and the low temperature activation energy decrease with increasing anion size. The results can be understood from the changing anion-cation interaction strength with changing anion size and from the energy landscape interpretation of the glass transition dynamics.

Phosphonium Ionic Liquid-Infused Poly(vinyl chloride) Surfaces Possessing Potent Antifouling Properties.

Microbial fouling is a costly issue, which impacts a wide range of industries, such as healthcare, food processing, and construction industries, and improved strategies to reduce the impact of fouling are urgently required. Slippery liquid-infused porous surfaces (SLIPSs) have recently been developed as a bioinspired approach to prevent antifouling. Here, we report the development of slippery, superhydrophilic surfaces by infusing roughened poly(vinyl chloride) (PVC) substrates with phosphonium ionic liquids (PILs). These surfaces were capable of reducing viable bacterial adherence by Staphylococcus aureus and Pseudomonas aeruginosa by >6 log10 cfu mL-1 after 24 h under static conditions relative to control PVC. Furthermore, we report the potential of a series of asymmetric quaternary alkyl PILs with varying alkyl chain lengths (C4-C18) and counteranions to act as antimicrobial agents against both Gram +ve and Gram -ve bacteria and illustrate their potential as antimicrobial alternatives to traditional fluorinated lubricants commonly used in the synthesis of SLIPSs.

Multicharge zwitterionic molecules: Hydration, kosmotropicity and anti-fouling potential.

This manuscript presents a comparative study of the physico-chemical behaviour of sulfobetaine-type single and double zwitterions and zwitterionic salts, and structurally similar mono- and di-cationic tetraalkylammonium salts in aqueous solutions. The study includes experimental determination of the density and viscosity of highly diluted aqueous solutions with derivation of the Jones-Dole viscosity B-coefficient, partial molal volumes at infinite dilution, and hydration numbers. The study also examines the effects of addition of the salts on the surface tension of cationic and anionic surfactants, upper critical solution temperature of a non-ionic surfactant, solubility of amino acids, and stability of a protein. The experimental investigation was performed taking a broad bottom-up approach with the aim to elucidate the effect of molecular architecture and charge (two versus four) on the degree of surface hydration of a molecule, kosmotropicity, and interactions with charged and hydrophilic/hydrophobic surfaces - all-important characteristics which define ability of a functional group to resist protein attachment. The novel multicharged zwitterionic materials have exhibited superior qualities, thus paving the way to development of a new platform in design of hydrophilic and anti-fouling surfaces by employing the four-charge bearing molecular motifs.