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][Tf2N]. 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 D-5(0) -> F-7(2) transition ( up to 15 times more intense than the D-5(0) -> F-7(1)) transition, whereas a marked feature of the PMMA films doped with [choline](3)[Eu(dpa)(3)] is the long lifetime of the D-5(0) excited state (1.8 ms).

Choline saccharinate and choline acesulfamate: Ionic liquids with low toxicities

Choline saccharinate and choline acesulfamate are two examples of hydrophilic ionic liquids, which can be prepared from easily available starting materials (choline chloride and a non-nutritive sweetener). The (eco)toxicity of these ionic liquids in aqueous solution is very low in comparison to other types of ionic liquids. A general method for the synthesis and purification of hydrophilic ionic liquids is presented. The method consists of a silver-free metathesis reaction, followed by purification of the ionic liquid by ion-exchange chromatography. The crystal structures show a marked difference in hydrogen bonding between the two ionic liquids, although the saccharinate and the acesulfamate anions show structural similarities. The optimized structures, the energetics, and the charge distribution of cation-anion pairs in the ionic liquids were studied by density functional theory (DFT) and second-order (Moller-Plesset) perturbation theory calculations. The occupation of the non-Lewis orbitals was considered to obtain a qualitative picture of the Lewis structures. The calculated interaction energies and the dipole moments for the ion pairs in the gas phase were discussed.

Visible-light-sensitized near-infrared luminescence from rare-earth complexes of the 9-hydroxyphenalen-1-one ligand

The unique absorption properties of the 9-hydroxyphenalen-1-one (HPHN) ligand have been exploited to obtain visible-light-sensitizable rare-earth complexes in 1: 3 and 1: 4 metal-to-ligand ratios. In both stoichiometries (1:3,tris,Ln(PHN)3;1:4, tetrakis, A[ Ln( PHN)(4)], with Ln being a trivalent rare-earth ion and A being a monovalent cation), the complexes of Nd(III),Er( III), and Yb(III) show typical near-infrared luminescence upon excitation with visible light with wavelengths up to 475 nm. The X-ray crystal structures of the tris complexes show solvent coordination to the central rare-earth ion, whereas in the tetrakis complexes, the four PHN-ligands form a protective shield around the central ion, preventing small solvent molecules from coordinating to the rare-earth ion, at least in the solid state.

Task-specific ionic liquid for solubilizing metal oxides

Protonated betaine bis(trifluoromethylsulfonyl) imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium( II) oxide, mercury( II) oxide, nickel( II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese( II) oxide, and silver( I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis( trifluoromethylsulfonyl) imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C ( temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis( trifluoromethylsulfonyl) imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.

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 Cl-35 NMR spectroscopies.

Pharmacology of transient receptor potential melastatin channels in the vasculature.

Mammalian transient receptor potential melastatin (TRPM) non-selective cation channels, the largest TRP subfamily, are widely expressed in excitable and non-excitable cells where they perform diverse functions ranging from detection of cold, taste, osmolarity, redox state and pH to control of Mg(2+) homeostasis and cell proliferation or death. Recently, TRPM gene expression has been identified in vascular smooth muscles with dominance of the TRPM8 channel. There has been in parallel considerable progress in decoding the functional roles of several TRPMs in the vasculature. This research on native cells is aided by the knowledge of the activation mechanisms and pharmacological properties of heterologously expressed TRPM subtypes. This paper summarizes the present state of knowledge of vascular TRPM channels and outlines several anticipated directions of future research in this area.

Small angle neutron scattering from 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids ([C(n)mim][PF6], n=4, 6, and 8)

The presence of local anisotropy in the bulk, isotropic, and ionic liquid phases-leading to local mesoscopic inhomogeneity-with nanoscale segregation and expanding nonpolar domains on increasing the length of the cation alkyl-substituents has been proposed on the basis of molecular dynamics (MD) simulations. However, there has been little conclusive experimental evidence for the existence of intermediate mesoscopic structure between the first/second shell correlations shown by neutron scattering on short chain length based materials and the mesophase structure of the long chain length ionic liquid crystals. Herein, small angle neutron scattering measurements have been performed on selectively H/D-isotopically substituted 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids with butyl, hexyl, and octyl substituents. The data show the unambiguous existence of a diffraction peak in the low-Q region for all three liquids which moves to longer distances (lower Q), sharpens, and increases in intensity with increasing length of the alkyl substituent. It is notable, however, that this peak occurs at lower values of Q (longer length scale) than predicted in any of the previously published MD simulations of ionic liquids, and that the magnitude of the scattering from this peak is comparable with that from the remainder of the amorphous ionic liquid. This strongly suggests that the peak arises from the second coordination shells of the ions along the vector of alkyl-chain substituents as a consequence of increasing the anisotropy of the cation, and that there is little or no long-range correlated nanostructure in these ionic liquids.

The electrochemical oxidation of catechol and dopamine on platinum in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF4]): Adsorption effects in ionic liquid voltammetry

The electrochemical oxidation of catechol and dopamine has been studied at a platinum micro-electrode (10 pm diameter) in two room temperature ionic liquids (RTILs): 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BE4]). For catechol in [C(2)mim][NTf2], an electrochemically quasi-reversible oxidation peak was observed at 1.1 V vs. Pt with a back peak at 0.4 V vs. Pt. This is assigned to the two-electron oxidation of catechol to doubly protonated o-benzoquinone. Double-step chronoamperometry gave a diffusion coefficient for the catechol and the oxidised species which is 3.8 x 10(-11) m(2) s(-1) for both. For catechol in [C(4)mim][BF4], a two-electron oxidation wave was observed at 1.0 V vs. Pt with no back peak. Another peak at less positive potential was also observed at 0.6 V vs. Pt in [C(4)mim][BF4] but not in [C(2)mim][NTf2] which is assigned to the adsorption of electrochemically formed neutral o-benzoquinone on the platinum electrode. The oxidised protonated o-benzoquinone is suggested to be deprotonated by the [BF4](-) anion, but not by the [NTf2](-) anion: hence adsorption of the neutral species at the platinum electrode, not the charged species. For dopamine in both RTILs, two chemically irreversible oxidation peaks were observed at 0.75 V and 1.1 V vs. Pt, and assigned to the oxidation of dopamine to the corresponding semi-quinone and the quinone. Potential-step chronoamperometry was carried out on the oxidation waves of dopamine in [C(2)mim][NTf2] and the diffusion coefficient of species in solution was calculated to be 6.85 x 10(-12) m(2) s(-1) and confirmed that the waves corresponded to one and two electron processes. A third wave was observed at 1.8 V vs. Pt which is attributed to the oxidation of the amine group to a radical cation with likely subsequent follow up chemistry. In [C(4)mim][BF4] a peak at less positive potential was observed for dopamine, similar to catechol which is assigned to the adsorption of the neutral quinone species on the platinum electrode formed by the reaction of the removal of protons from the oxidised dopamine with the [BF4](-) anion. (C) 2009 Elsevier B.V. All rights reserved.

Interfacial tensions of imidazolium-based ionic liquids with water and n-alkanes

The interfacial tension of the liquid-liquid phase boundary of several 1,3-dialkyl imidazolium based ionic liquids, namely, 1,3-dimethylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C(1)mim][NTf2], 1-ethyl-3-methylimidazoliurn bis{(trifluoromethyl)sulfonyl}imide [C(2)mim][NTf2], 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C(4)mim][NTf2], 1-hexyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C(6)mim][NTf2], 1-octyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C(8)mim][NTf2], 1-butyl-3-methylimidazolium trifluoromethylsulfonate [C(4)mim][CF3SO3], and 1-butyl-3-methylimidazolium trifluoroacetate [C(4)mim][CF3COO] with water and with the n-alkanes, n-hexane, n-octane and n-decane, has been measured using the pendant drop method as a function of temperature from 293 to 323 K. The experimental interfacial tension data were correlated using the ionic liquid parachor estimation method and a mutual solubility model. The influence of the cation and anion of ionic liquids and also of alkyl chain length of n-alkanes on interfacial tension is discussed. It has also been demonstrated that the interfacial tension data estimated by the correlation methods are in good agreement with the experimental data. (C) 2010 Elsevier B.V. All rights reserved.

Selecting Room-Temperature Ionic Liquids to Optimize Voltammetric Responses: The Oxidation of NADH

The electrochemistry of nicotinamide adenine dinucleotide (NADH) in its reduced form was examined in two room-temperature ionic liquids (RTILs): 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and 1-butyl-3-methylimidazolium hexafluorophos-phate ([C(4)mim][PF6]). NADH oxidation has previously been studied in aqueous solution where it follows the pathway: one-electron oxidation to the NADH(center dot+) radical cation, deprotonation to produce the neutral NAD(center dot) radical, then oxidation to the NAD(+) cation. The electrochemistry of NADH was examined in [C(2)mim][NTf2] and [C(4)mim][PF6] at the bare Pt electrode (10 mu m diameter): In [C(2)mim][NTf2], no oxidation was observed; in [C(4)mim][PF6], an oxidative signal was observed, which likely followed the pathway described above, where upon formation of the NADH(center dot+) radical cation, the [PF6](-) anion (unlike the [NTf2](-) anion) reacts with the proton to form HPF6, which decomposes. This demonstrates the tunability of RTILs, whereby the choice of one anion in an RTIL over another can promote a reaction. Poly(vinylferrocene) (PVF) was studied as a mediator for the NADH detection in both RTILs to attempt to lower the potential of NADH detection. The Pt electrode was modified with PVF, and the oxidation of PVF to PVF+ was observed in [C(2)mim][NTf2] and [C(4)mim][PF6], but no mediation of the NADH oxidation was observed.

Solid and liquid charge-transfer complex formation between 1-methylnaphthalene and 1-alkyl-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide ionic liquids

Liquid charge-transfer (CT) complexes were observed to form on contacting electron-rich aromatics with electron withdrawing group appended 1-alkyl-4-cyanopyridinium ionic liquids (ILs). Cooling below the melting point of the ionic liquid resulted in crystallisation of ionic liquid from the complex for 2-cyano and 3-cyano pyridinium isomers and in the formation of a 1 : 1 IL : aromatic crystalline CT-complex with the 4-cyanopyridinium isomer. The liquid structure of a 1 : 1 mixture of 1-methyl-4-cyanopyridinium bis{(trifluoromethyl)sulfonyl} imide with 1-methylnaphthalene has been probed by neutron diffraction experiments and molecular dynamics simulations. A high degree of correlation between the experimental data and the simulations was found with a significant displacement of the anions from around the cation by the aromatic species and the resulting structure having pi-pi stacks between the cations and the aromatic.

The electrochemical reduction of the purines guanine and adenine at platinum electrodes in several room temperature ionic liquids

The reduction of guanine was studied by microelectrode voltammetry in the room temperature ionic liquids (RTILs) N-hexyltriethylammonium his (trifluoromethanesulfonyl) imide [N-6.2.2.2][N(Tf)(2)], 1-butyl-3-methylimidazolium hexafluorosphosphate [C(4)mim] [PF6], N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide [C(4)mpyrr][N(Tf)(2)], 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C-4mim][N(TF)(2)], N-butyl-N-methyl-pyrrolidinium dicyanamide [C(4)mpyrr][N(NC)(2)] and tris(P-hexyl)-tetradecylphosphonium trifluorotris(pentafluoroethyl)phosphate [P-14,P-6,(6,6)][FAP] on a platinum microelectrode. In [N-6,N-2,N-2,N-2][NTf2] and [P-14,P-6,P-6.6][FAP], but not in the other ionic liquids studied, guanine reduction involves a one-electron, diffusion-controlled process at very negative potential to produce an unstable radical anion. which is thought to undergo a dimerization reaction, probably after proton abstraction from the cation of the ionic liquid. The rate of this subsequent reaction depends on the nature of the ionic liquid, and it is faster in the ionic liquid [P-14,P-6,P-6.6[FAP], in which the formation of the resulting dimer can be voltammetrically monitored at less negative potentials than required for the reduction of the parent molecule. Adenine showed similar behaviour to guanine but the pyrimidines thymine and cytosine did not; thymine was not reduced at potentials less negative than required for solvent (RTIL) decomposition while only a poorly defined wave was seen for cytosine. The possibility for proton abstraction from the cation in [N-6,N-2,N-2,N-2],[NTF2] and [P-14,P-6,P-6.6][FAP] is noted and this is thought to aid the electrochemical dimerization process. The resulting rapid reaction is thought to shift the reduction potentials for guanine and adenine to lower values than observed in RTILs where the scope for proton abstraction is not present. Such shifts are characteristic of so-called EC processes where reversible electron transfer is followed by a chemical reaction. (C) 2009 Elsevier B.V. All rights reserved.

Mixing of dielectronic and multiply-excited states in electron-ion recombination: a study of Au24+

It has been suggested (Gribakin et al 1999 Aust. J. Phys. 52 443–57, Flambaum et al 2002 Phys. Rev. A 66 012713) that strongly enhanced low-energy electron recombination observed in Au25+ (Hoffknecht et al 1998 J. Phys. B: At. Mol. Opt. Phys. 31 2415–28) is mediated by complex multiply excited states, while simple dielectronic excitations play the role of doorway states for the electron capture process. We present the results of an extensive study of con?guration mixing between doubly excited (doorway) states and multiply excited states which account for the large electron recombination rate on Au25+ . A detailed analysis of spectral statistics and statistics of eigenstate components shows that the dielectronic doorway states are virtually ‘dissolved’ in complicated chaotic multiply excited eigenstates. This work provides a justi?cation for the use of statistical theory to calculate the recombination rates of Au25+ and similar complex multiply charged ions. We also investigate approaches which allow one to study complex chaotic many-body eigenstates and criteria of strong con?guration mixing, without diagonalizing large Hamiltonian matrices.

Bridging the Gap between Ionic Liquids and Molten Salts: Group 1 Metal Salts of the Bistriflamide Anion in the Gas Phase

Fourier transform ion cyclotron resonance mass spectrometry experiments showed that liquid Group 1 metal salts of the bistriflamide anion undergoing reduced-pressure distillation exhibit a remarkable behavior that is in transition between that of the vapor-liquid equilibrium characteristics of aprotic ionic liquids and that of the Group 1 metal halides: the unperturbed vapors resemble those of aprotic ionic liquids, in the sense that they are essentially composed of discrete ion pairs. However, the formation of large aggregates through a succession of ion-molecule reactions is closer to what might be expected for Group I metal halides. Similar experiments were also carried out with bis{(trifluoromethyl)sulfonyl}amine to investigate the effect of H+, which despite being the smallest Group 1 cation, is generally regarded as a nonmetal species. In this case, instead of the complex ion-molecule reaction pattern found for the vapors of Group I metal salts, an equilibrium similar to those observed for aprotic ionic liquids was observed.

Ionic Liquids Containing Boron Cluster Anions

The combination of different boron cluster anions and some of the cations typically found in the composition of ionic liquids has been possible by straightforward metathetic reactions, producing new low melting point salts; the imidazolium cations have been systematically studied, [C(n)mim](+) (when [C(n)mim](+) = 1-alkyl-3-methylimidazolium; n = 2, 4, 6, 8, 10, 12, 14, 16, or 18). Melting points increase in the anionic order [Co(C2B9H11)(2)](-) =-34 degrees C). The salts [C(n)mim](2)[X] ([X](2-) = [B10Cl10](2-) or [B12Cl12](2-), n = 16 or 18) show liquid crystal phases between the solid and liquid states. Tetraalkylphosphonium salts of [B10Cl10](2-) have also been prepared. Physical properties, such as thermal stability, density, or viscosity, have been measured for some selected samples. The presence of the perhalogenated dianion [B12Cl12](2-) in the composition of the imidazolium salts renders highly thermally stable compounds. For example, [C(2)mim](2)[B12Cl12] starts to decompose above 480 degrees C in a dynamic TGA analysis under a dinitrogen atmosphere. Crystal structures of [C(2)mim][Co(C2B9H11)(2)] and [C(2)mim](2)[B12Cl12] have been determined. H-1 NMR spectra of selected imidazolium-boron cluster anion salts have been recorded from solutions as a function of the concentration, showing trends related to the cation-anion interactions.