Phosphine oxide functionalised imidazolium ionic liquids as tuneable ligands for lanthanide complexation

A series of novel, phosphine oxide functionalised ionic liquids have been synthesised and their application as tuneable lanthanide complexing agents is demonstrated.

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, chi(SnCl2), was investigated in both solid and liquid states. The room temperature ionic liquids were investigated by Sn-119 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 [SnCl3](-) in equilibrium with Cl- when chi(SnCl2) < 0.50, [SnCl3](-) in equilibrium with [Sn2Cl5](-) when chi(SnCl2) > 0.50, and only [SnCl3](-) when chi(SnCl2) = 0.50. Tin(II) chloride was found to precipitate when chi(SnCl2) > 0.63. No evidence was detected for the existence of [SnCl4](-) across the entire range of chi(SnCl2) 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, chi(SnCl2), to reveal Lewis acidity for chi(SnCl2) > 0.50 samples comparable to the analogous systems based on zinc(II). A change of the Lewis basicity of the anion was estimated using H-1 NMR spectroscopy, by comparison of the measured chemical shifts of the C-2 hydrogen in the imidazolium ring. Finally, compositions containing free chloride anions (chi(SnCl2) < 0.50) were found to oxidize slowly in air to form a chlorostannate(IV) ionic liquid containing the [SnCl6](2-) anion.

High-pressure volumetric properties of imidazolium-based ionic liquids: Effect of the anion

The densities of five imidazolium-based ionic liquids (ILs) (1-butyl-3-methylimidazolium tetrafluoroborate, [CiC4-Im][BF 4]; 1-butyl-3-methylimidazolium hexafluorophosphate, [CiC 4Im][PF6]; 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [C1C4Im][Tf 2N]; 1-ethyl-3-methylimidazoliumbis{(trifluoromethyl)sulfonyl}-imide, [C1C2Im][Tf2N]; l-ethyl-3-methylimidazolium ethylsulfate, [C1C2Im][EtSO4]) were measured as a function of temperature from (293 to 415) K and over an extended pressure range from (0.1 to 40) MPa using a vibratingtube densimeter. Knowledge of the variation of the density with temperature and pressure allows access to the mechanical coefficients: thermal expansion coefficient and isothermal compressibility. The effects of the anion and of the length of the alkyl chain on the imidazolium ring on the volumetric properties were particularly examined. The mechanical coefficients were compared with those of common organic solvents, water and liquid NaCl. Finally, a prediction model, based on an "ideal" volumetric behavior of the ILs, is proposed to allow calculation of the molar volume of imidazolium-based ionic liquids as a function of temperature. ©2007 American Chemical Society.

Comments and Additional Work on “High-Pressure Volumetric Properties of Imidazolium-Based Ionic Liquids: Effect of the Anion”

This works follows a publication of our group in J. Chem. Eng. Data2007, 52, 2204–2211 presenting high temperature and pressure density data for five imidazolium-based ionic liquids. At this period, very few ionic liquid density data were available in the literature, especially at high pressure, and the uncertainty of published results was calculated with respect to the literature data available for three of the five ionic liquids studied. Since 2007, the ionic liquid density databank has largely increased. In this work, a comparison of our published data in J. Chem. Eng. Data2007, 52, 2204–2211, with more than 1800 high pressure data coming from the literature up to December 2011 is presented to assess the uncertainty of our published values. The claimed uncertainty is close to 0.31 % for all IL density data sets except in the case of the [C1C2Im][EtSO4], where the uncertainty is up to 1.1 %. Reported data in J. Chem. Eng. Data2007, 52, 2204–2211, for this particular ionic liquid cannot be used as a reference. For this ionic liquid, new density measurements of the same sample batch have been remeasured by using the same experimental technique, and new experimental data presented herein are clearly higher than our previous published results. A 1H NMR analysis of the sample has confirmed hydrolysis of the ethylsulfate anion to ethanol and hydrogenate anion which explains the differences observed between our density data and the literature.

Enhanced antimicrobial activities of 1-alkyl-3-methyl imidazolium ionic liquids based on silver or copper containing anions

We have developed a series of 1-alkyl-3-methylimidazolium tetrachlorocuprate(II) and dibromoargentate(I) ionic liquids with enhanced antimicrobial activity when compared with 1-alkyl-3-methylimidazolium chloride ionic liquids. These new ionic liquids proved to be effective against a range of pathogenic bacteria and fungi.

Chiral thiouronium salts: synthesis, characterisation and application in NMR enantio-discrimination of chiral oxoanions

Chiral thioureas and functionalised chiral thiouronium salts were synthesised starting from the relatively cheap and easily available chiral amines: (S)-methylbenzylamine and rosin-derived (+)-dehydroabietylamine. The introduction of a delocalised positive charge to the thiourea functionality, by an alkylation reaction at the sulfur atom, enables dynamic rotameric processes: hindered rotations about the delocalised CN and CS bonds. Hence, four different rotamers/isomers may be recognised: syn-syn, syn-anti, anti-syn and anti-anti. Extensive H-1 and C-13 NMR studies have shown that in hydrogen-bond acceptor solvents, such as perdeuteriated dimethyl sulfoxide, the syn-syn conformation is preferable. On the other hand, when using non-polar solvents, such as CDCl3, the mixture of syn-syn and syn-anti isomers is detectable, with an excess of the latter. Apart from this, in the case of S-butyl-N,N'-bis(dehydroabietyl)thiouronium ethanoate in CDCl3, the H-1 NMR spectrum revealed that strong bifurcated hydrogen bonding between the anion and the cation causes global rigidity without signs of hindered rotamerism observable on the NMR time scale. This suggested that these new salts might be used as NMR discriminating agents for chiral oxoanions, and are indeed more effective than their archetypal guanidinium analogues or the neutral thioureas. The best results in recognition of a model substrate, mandelate, were obtained with S-butyl-N,N'-bis(dehydroabietyl) thiouronium bistriflamide. It was confirmed that the chiral recognition occurred not only for carboxylates but also for sulfonates and phosphonates. Further H-1 NMR studies confirmed a 1 : 1 recognition mode between the chiral agent (host) and the substrate (guest); binding constants were determined by H-1 NMR titrations in solutions of DMSO-d(6) in CDCl3. It was also found that the anion of the thiouronium salt had a significant influence on the recognition process: anions with poor hydrogen-bond acceptor abilities led to the best discrimination. The presence of host-guest hydrogen bonding was confirmed in the X-ray crystal structure of S-butyl-N,N'-bis(dehydroabietyl)thiouronium bromide and by computational studies (density functional theory).

A Neutron Diffraction and Molecular Dynamics Investigation of Acetate-based Ionic Liquids as Solvents for Glucose

The liquid state structure of the ionic liquid, 1-ethyl-3-methylimidazolium acetate, and the solute/solvent structure of glucose dissolved in the ionic liquid at a 1: 6 molar ratio have been investigated at 323 K by molecular dynamics simulations and neutron diffraction experiments using H/D isotopically substituted materials. Interactions between hydrogen-bond donating cation sites and polar, directional hydrogen-bond accepting acetate anions are examined. Ion-ion radial distribution functions for the neat ionic liquid, calculated from both MD and derived from the empirical potential structure refinement model to the experimental data, show the alternating shell-structure of anions around the cation, as anticipated. Spatial probability distributions reveal the main anion-to-cation features as in-plane interactions of anions with imidazolium ring hydrogens and cation-cation planar stacking. Interestingly, the presence of the polarised hydrogen-bond acceptor anion leads to increased anion-anion tail-tail structuring within each anion shell, indicating the onset of hydrophobic regions within the anion regions of the liquid.

High pressure CO2 absorption studies on imidazolium-based ionic liquids:Experimental and simulation approaches

A combined experimental-computational study on the CO absorption on 1-butyl-3-methylimidazolium hexafluophosphate, 1-ethyl-3-methylimidazolium bis[trifluoromethylsulfonyl]imide, and 1-butyl-3-methylimidazolium bis[trifluoromethylsulfonyl]imide ionic liquids is reported. The reported results allowed to infer a detailed nanoscopic vision of the absorption phenomena as a function of pressure and temperature. Absorption isotherms were measured at 318 and 338K for pressures up to 20MPa for ultrapure samples using a state-of-the-art magnetic suspension densimeter, for which measurement procedures are developed. A remarkable swelling effect upon CO absorption was observed for pressures higher than 10MPa, which was corrected using a method based on experimental volumetric data. The experimental data reported in this work are in good agreement with available literature isotherms. Soave-Redlich-Kwong and Peng-Robinson equations of state coupled with bi-parametric van der Waals mixing rule were used for successful correlations of experimental high pressure absorption data. Molecular dynamics results allowed to infer structural, energetic and dynamic properties of the studied CO+ionic liquids mixed fluids, showing the relevant role of the strength of anion-cation interactions on fluid volumetric properties and CO absorption. © 2012 Elsevier B.V.

Understanding the Effects of Ionicity in Salts, Solvates, Co-Crystals, Ionic Co-Crystals, and Ionic Liquids, Rather than Nomenclature, Is Critical to Understanding Their Behavior

The incorporation of active pharmaceutical ingredients (APIs) into multicomponent solid forms (such as salts and co-crystals) or liquid forms (such as ionic liquids (ILs) or deep eutectic mixtures) is important in optimizing the efficacy and delivery of APIs. However, there is a current debate regarding the classification of these multicomponent systems based on their ionicity which could interfere with their consideration in important applications. Multicomponent systems of intermediate ionicity can show a combination of properties, leading to behavior that is neither strictly typical of either purely ionic or purely neutral compounds, nor easily described as intermediate between the two. In this perspective, we attempt to illustrate the problems in classifying multicomponent APIs based on one of two categories by discussing selected literature regarding solid and liquid multicomponent APIs and presenting the crystal structures of some relevant systems as case studies. It is clear that a focus on restrictive nomenclature carries with it the risk that a thorough examination of the physicochemical properties of the compounds will be overlooked.

Viscous behavior of imidazolium-based ionic liquids

The viscosity of four imidazolium-based ionic liquids is analyzed as a function of pressure and temperature. Experimental measurements were carried out using an electromagnetic moving piston viscometer in the 303-353 K and 0.1-70 MPa ranges on synthesized ultrapure samples, and compared with available literature data. Molecular dynamics simulations were used to analyze the fluids' dynamic properties from a nanoscopic viewpoint, with special attention paid to self-diffusion coefficients and dynamic viscosity. Simulated properties are in excellent agreement with experimental results in spite of the glasslike dynamics of some of the studied fluids. © 2013 American Chemical Society.

Bioatividade de Líquidos Iónicos derivados do Ácido Valpróico em bactérias Gram-negativa

Os Líquidos Iónicos (LIs) são sais orgânicos constituídos exclusivamente por iões e possuem pontos de fusão inferiores a 100ºC. As suas propriedades únicas e o facto de ser possível ajustar as suas propriedades físicas, químicas e biológicas, de acordo com o objetivo pretendido, tornam esta classe de compostos, um grande objeto de estudo de inúmeros investigadores. Desde os inícios da sua aplicação até à atualidade, a investigação nesta área expandiu o seu raio de ação, estando já descrito o seu potencial como agentes antimicrobianos e, mais recentemente, como compostos farmacêuticos ativos. Atualmente muitas das suas aplicações são baseadas nas suas propriedades biológicas. Esta Tese teve como objetivo avaliar a influência que os LIs podem exercer a nível do crescimento bacteriano e estudar alternativas de combater a resistência bacteriana. Todos os LIs utilizados neste trabalho tinham como anião o ácido valpróico, sendo utilizados catiões orgânicos de amónio e de imidazólio. Foram utilizadas 4 bactérias e avaliou-se a atividade biológica e a respetiva taxa de crescimento. O estudo da sua atividade biológica foi feito através da determinação da Concentração Mínima Inibitória (CMI) e a análise das suas curvas de crescimentos na presença e ausência de composto. Com este trabalho foi possível verificar que dentro dos compostos em estudo, LIs derivados do valproato, o Valproato com o cetilperidínio [valp] [cetylpir] foi o que influenciou o crescimento de todas as bactérias estudadas. Este estudo demonstrou o potencial antibacteriano de alguns compostos, podendo desta forma vir a ser utilizados para fins farmacêuticos