New catanionic surfactants based on 1-alkyl-3-methylimidazolium alkylsulfonates, [C(n)H(2n+1)mim][CmH2m+1SO3]: mesomorphism and aggregation

Anionic and cationic alkyl-chain effects on the self-aggregation of both neat and aqueous solutions of 1-alkyl-3-methylimidazolium alkylsulfonate salts ([C(n)H(2n+ 1)mim][CmH2m+1SO3]; n = 8, 10 or 12; m = 1 and n = 4 or 8; m = 4 or 8) have been investigated. Some of these salts constitute a novel family of pure catanionic surfactants in aqueous solution. Examples of this class of materials are rare; they are distinct from both mixed cationic-anionic surfactants (obtained by mixing two salts) and gemini surfactants (with two or more amphiphilic groups bound by a covalent linker). Fluorescence spectroscopy and interfacial tension measurements have been used to determine critical micelle concentrations (CMCs), surface activity, and to compare the effects of the alkyl-substitution patterns in both the cation and anion on the surfactant properties of these salts. With relatively small methylsulfonate anions (n = 8, 10 and 12, m = 1), the salts behave as conventional single chain cationic surfactants, showing a decrease of the CMC upon increase of the alkyl chain length (n) in the cation. When the amphiphilic character is present in both the cation and anion (n = 4 and 8, m = 4 and 8), novel catanionic surfactants with CMC values lower than those of the corresponding cationic analogues, and which exhibited an unanticipated enhanced reduction of surface tension, were obtained. In addition, the thermotropic phase behaviour of [C(8)H(18)mim][C8H18SO3] (n = m = 8) was investigated using variable temperature X-ray scattering, polarising optical microscopy and differential scanning calorimetry; formation of a smectic liquid crystalline phase with a broad temperature range was observed.

A simple colorimetric method for the quality control of 1-alkyl-3-methylimidazolium ionic liquid precursors

A simple colorimetric method to monitor the production of ionic liquid precursors is developed, which is based on the determination of 1-methylimidazole with copper(II) chloride. The synthesis of 1-ethyl-3-methylimidazolium chloride, an industrially important ionic liquid precursor, can be followed and the purity of the final product can be readily assessed in a quick and convenient manner.

Using Caenorhabditis elegans to probe toxicity of 1-alkyl-3-methylimidazolium chloride based ionic liquids

Ionic liquids are gaining attention as new solvents within the green chemistry community; however this attention has quickly outstripped current environmental and toxicological data available. In the present communication, we establish the use of Caenorhabditis elegans as a model organism for inexpensively and quickly exploring toxicological effects of 1-alkyl-3-methylimidazolium chloride ionic liquids.

Study of the transamidative ring expansion of N--halogenoalkyl--lactams of alkyl chain lengths 2–12 in liquid ammonia and other liquid amines: syntheses of 7-, 8- and 9-membered 1,5-diaza cyclic ketones, including routes to (±)-dihydroperiphylline and (±)-celabenzine

N-(3-Halogenopropyl)-4-phenylazetidin-2-ones undergo amination in liquid ammonia followed by transamidative ring expansion to give the eight-membered 4-phenyl -1,5-diazacyclooctan-2-one in excellent yield. Ring expansion of the amines in liquid ammonia is found to be much more effective than in hydrocarbon solvents. Formation of 7-, 8-, and 9-membered azalactams from the requisite -halogenoalkyl--lactams is an excellent synthetic process, though it is not applicable to 10membered rings. In the cases of rings of 13-, 15- and 17-members, although amination and apparent expansion takes place, the large rings appear not to be stable to ammonia and the final products are acyclic amides. N-[4-Halogenobut-2(Z)-enyl]-4-phenylazetidin-2-one satisfactorily forms a 9-membered (Z)-olefinic azalactam, but the (E)-isomer gives an acyclic amino amide. By using alkyl-substituted -lactam side-chains, C-substituted medium rings can be obtained; the relative instability of N-acyl -lactams to ammonia, however, leads to acylamino amides rather than expanded rings.Employing ethylamine in place of ammonia, it is shown that N-ethylated azalactams are formed satisfactorily, and using allylamine, N-allyl medium rings capable of further elaboration are obtained. The chemistry of these systems is discussed. Using transamidation in liquid ammonia, a short synthesis of the 9-membered spermidine alkaloid (±)-dihydroperiphylline is reported. Synthesis of key intermediates, whose transformation into the 13-membered alkaloids of the celabenzine group has already been effected, has been carried out.X-Ray single-crystal structure determinations for 4-phenyl-1,5-diazacyclononan-2-one, trans-4-phenyl-8-methyl-1,5-diazacyclooctan-2-one and (Z)-4-phenyl-1,5-diazacyclonon-7-en-2-one are reported, and comment is made on certain conformational features.

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.

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.

Antibiofilm activities of 1-alkyl-3-methylimidazolium chloride ionic liquids

Microbial biofilms are ubiquitous in nature and represent the predominant mode of growth of microorganisms. A general characteristic of biofilm communities is that they tend to exhibit significant tolerance to antimicrobial challenge compared with planktonic bacteria of the same species The antibiofilm activity of a series of 1-alkyl-3-methylimidazolium chloride ionic liquids has been evaluated against a panel of clinically significant microbial pathogens, including MRSA. A comparison of antimicrobial activity against planktonic bacteria and established biofilms is presented. In general, these ionic liquids possess potent, broad spectrum antibiofilm activity.

Antimicrobial and antibiofilm activities of 1-alkylquinolinium bromide ionic liquids

Quinoline derivatives are known to possess a range of bioactive and medicinal activities, which have been exploited in the design of antibacterial, antifungal and antimalarial compounds. In this study, we report on the microbiological toxicity of a series of 1-alkylquinolinium bromides against a range of clinically relevant microorganisms, in both planktonic and sessile (biofilm) cultures. A comparison of antimicrobial activity against planktonic bacteria and established biofilms is presented. In general, 1-alkylquinolinium ionic liquids possess excellent, broad spectrum antimicrobial activity against microorganisms grown in both the planktonic and sessile, or biofilm, mode of growth. Importantly, these compounds are potent against Gram positive and Gram negative bacteria, as well as fungi, with a clear dependency on length of the alkyl substituent for activity, with compounds containing twelve and fourteen carbons in the alkyl group exhibiting highest antimicrobial and antibiofilm activity. © 2010 The Royal Society of Chemistry.

TIME-RESOLVED ABSORPTION, INFRARED, AND RESONANCE RAMAN-SPECTRA OF THE COMPLEXES [RU(X)(R)(CO)(2)(ALPHA-DIIMINE)] (X=HALIDE R=ALKYL) - INFLUENCE OF X ON THE CHARGE-TRANSFER CHARACTER OF THE LOWEST EXCITED-STATE

Nanosecond time-resolved absorption (TA), resonance Raman (TR(3)), and infrared (TRIR) spectra are reported for several complexes [Ru(X)(R)(CO)(2)(alpha-diimine)] (X = Cl, Br, I; R = Me, Et; alpha-diimine = N,N'-diisopropyl-1,4-diaza-1,3-butadiene (iPr-DAB), pyridine-2-carbaldehyde-N-isopropylimine (iPr-PyCa), 2,2'-bipyridine (bpy)). This is the first instance in which the TA, TR(3), and TRIR techniques have been used to probe excited states in the same series of complexes. The TA spectra of the iodide complexes show a transient absorption between 550 and 700 nm, which does not depend on the solvent but shifts to lower energy in the order iPr-DAB > bpy > iPr-PyCa. This band is assigned to an intraligand transition. For the corresponding chloride and bromide complexes this band occurs at higher energy, most probably because of a change of character of the lowest excited state from XLCT to MLCT. The TRIR spectra show an increase in v(CO) (and k(CO)) on promotion to the excited state; however, the shifts Delta v(CO) show a decrease in the order Cl- > Br- > I-. The TR(3) spectra of the excited complexes [Ru(X)(R)(Co)(2)(iPr-DAB)] show v(s)(CN) of the iPr-DAB ligand 50-80 cm(-1) lower in frequency than for the complexes in their ground state. This frequency shift decreases in the order Cl- > Br- > I-, indicating a decrease of CT character of the lowest excited state in this order. However, going from X = Br to I, the effect on Delta v(CO) is much larger than the decrease of Delta v(s)(CN). This different effect on the CO- and CN-stretching frequencies is assigned to a gradual change in character of the lowest excited state from MLCT to XLCT when Cl- is replaced by Br- and I-. This result confirms a similar conclusion derived from previous resonance Raman and emission experiments on these complexes.

Toluene and naphthalene dioxygenase-catalysed sulfoxidation of alkyl aryl sulfides

A series of alkyl aryl sulfides were metabolised, using selected strains of the soil bacterium Pseudomonas putida containing either toluene dioxygenase (TDO) or naphthalene dioxygenase (NDO), to give chiral sulfoxides. Alkyl aryl sulfoxides 2a-2k, 4a-4j and 4l, having enantiomeric excess (ee) values of >90%, were obtained by use of the appropriate strain of P. putida (UV4 or NCIMB 8859), Enantiocomplimentarity was observed for the formation of sulfoxides 2a, 2b, 2d, 2j, 4a, 4b and 4d, with TDO-catalysed (UV4) oxidation favouring the (R) enantiomer and NDO-catalysed oxidation (NCIMB 8859) the (S) enantiomer. Evidence of involvement of the TDO enzyme was obtained using a recombinant strain of Escherichia coli (pKST 11), The marked degree of stereoselectivity appears to be mainly due to enzyme-catalysed asymmetric sulfoxidation, however the possibility of a minor contribution from kinetic resolution, in some cases, cannot be excluded.

1-Alkyl-3-methylimidazolium alkanesulfonate ionic liquids, [C(n)H(2n+1)mim][CkH2k+1SO3]: synthesis and physicochemical properties

A set of 1-alkyl-3-methylimidazolium alkanesulfonate ionic liquids, [C(n)mim][CkSO3], formed by the variation of the alkyl chain lengths both in the cation and the anion (n = 1-6, 8, or 10; k = 1-4, or 6), was synthesised, with sixteen of them being novel. The ionic liquids were characterised by H-1 and C-13 NMR spectroscopy, and mass spectrometry. Their viscosities and densities as a function of temperature, as well as melting points and decomposition temperatures, were determined. The molecular volumes, both experimental and calculated, were found to depend linearly on the sum (n + k).

Isolation and Characterisation of 1-Alkyl-3- Methylimidazolium Chloride Ionic Liquid-Tolerant and Biodegrading Marine Bacteria

The aim of this study was to isolate and identify marine-derived bacteria which exhibited high tolerance to, and an ability to biodegrade, 1-alkyl-3-methylimidazolium chloride ionic liquids. The salinity and hydrocarbon load of some marine environments may induce selective pressures which enhance the ability of microbes to grow in the presence of these liquid salts. The isolates obtained in this study generally showed a greater ability to grow in the presence of the selected ionic liquids compared to microorganisms described previously, with two marine-derived bacteria, Rhodococcus erythropolis and Brevibacterium sanguinis growing in concentrations exceeding 1 M 1-ethyl-3-methylimidazolium chloride. The ability of these bacteria to degrade the selected ionic liquids was assessed using High Performance Liquid Chromatography (HPLC), and three were shown to degrade the selected ionic liquids by up to 59% over a 63-day test period. These bacterial isolates represent excellent candidates for further potential applications in the bioremediation of ionic liquid-containing waste or following accidental environmental exposure.