Mark Nieuwenhuyzen

Crystal polymorphism in 1-butyl-3-methylimidazolium halides: supporting ionic liquid formation by inhibition of crystallizationElectronic supplementary information (ESI) available: packing diagrams for I and II; table of closest contacts for I, I-Br and II. See http://www.rsc.org/suppdata/cc/b3/b304543a/

Crystallization of 1-butyl-3-methylimidazolium chloride from mixed ionic liquid or ionic liquid–aromatic solution, and from the melt yields different crystalline polymorphs, the first direct evidence for inhibition of crystallization in ionic liquids by polymorphism.

Liquid clathrate formation in ionic liquid-aromatic mixtures

1-Alkyl-3-methylimidazolium containing ionic liquids with hexafluorophosphate, bis(trifyl)imide, tetrafluoroborate, and chloride anions form liquid clathrates when mixed with aromatic hydrocarbons; in the system 1,3-dimethylimidazolium hexafluorophosphate-benzene, the aromatic solute could be trapped in the solid state forming a crystalline 2:1 inclusion compound.

Liquid structure of 1, 3-dimethylimidazolium salts

The structure of liquid 1, 3-dimethylimidazolium hexafluorophosphate is described in detail and compared with the structure of 1, 3-dimethylimidazolium chloride. In each case, the data were obtained from neutron diffraction experiments and analysed using an empirical potential structure refinement process. Overall, the structures are similar; however, significant differences arise from the variation in anion size.

The Formation of Luminescent Supramolecular Ternary Complexes in Water: Delayed Luminescence Sensing of Aromatic Carboxylates Using Coordinated Unsaturated Cationic Heptadentate Lanthanide Ion Complexes

The synthesis of four lanthanide ion complexes Eu•1, Eu•2, Tb•1 and Tb•2, from the heptadentate tri-arm cyclen (1,4,7,10-tetraazacyclododecane) ligands 1 and 2 that were made in one-pot syntheses is described. These coordinatively unsaturated complexes have two labile metal-bound water molecules, as demonstrated by X-ray crystallography. This was also confirmed by evaluating their hydration state (q∼2) by measuring their lifetimes in D2O and H2O, respectively. The above complexes were all designed as being “photophysically silent” prior to the recognition of the anion, since they do not possess antenna that can participate in sensitisation of the Eu(III) or the Tb(III) excited state. However, the two water molecules can be displaced upon anion binding by the appropriate aromatic carboxylates to give ternary complexes in water, through either four- or six-member ring chelates (q∼0), or possibly via a monodentate binding. In the case of Tb•1 and Tb•2, large luminescence enhancements were observed upon the formation of such ternary complexes with N,N-dimethylaminobenzoic acid at ambient pH. Such binding and luminescent enhancements were also observed for Tb•1 in the presence of salicylic acid. On all occasions, the anion recognition “switched” the emission “on” over two logarithmic units. At higher concentrations, the emission is reduced possibly due to quenching. In the case of aspirin, the binding was too weak to be measured, indicating that Tb•1 selectively detects salicylic acid, the active form of aspirin in water. In the case of Eu•1 and Eu•2, the affinity of these complexes towards such aromatic carboxylates was too weak for efficient ternary complex formation. Various carboxylic-acid-based antennae tested.

Molecular layering and local order in thin films of 1-alkyl-3-methylimidazolium ionic liquids using X-ray reflectivity

X-ray reflectivity measurements in air of thin films of 1-alkyl-3-methylimidazolium salts in the liquid, liquid crystalline and solid states supported on Si(111) are described. The films show Bragg features in both liquid crystalline and solid phases, but only after an initial annealing cycle. Kiessig fringes are observed only for the 1-octadecyl-3-methyl-imidazolium hexafluorophosphate films and, following analysis using Parratt32, a bi-layer model is proposed whereby the molecules are orientated with ionic groups at both salt-air and salt-silicon interfaces.

Ring-Opening Polymerisation of Silver–Diphosphine [M2L3] Coordination Cages To Give [M2L3]∞ Coordination Polymers

[M2L3] coordination cages and linear [M2L3]∞ polymers of the rigid, bridging diphosphines bis(diphenylphosphino)acetylene (dppa) and trans-1,2-bis(diphenylphosphino)ethylene (dppet) with silver(I) salts have been investigated in the solution and solid states. Unlike flexible diphosphines, 1:1 dppa/AgX mixtures do not selectively form discrete [Ag2(diphos)2(X)2] macrocycles; instead dynamic mixtures of one-, two- and three-coordinate complexes are formed. However, 3:2 dppa/AgX ratios (X=SbF6, BF4, O3SCF3 or NO3) do lead selectively to new [M2L3] triply bridged cage complexes [Ag2(dppa)3(X)2] 1 a–d (X=SbF6a, BF4b, O3SCF3c, NO3d), which do not exhibit Ag−P bond dissociation at room temperature on the NMR time scale (121 MHz). Complexes 1 a–d were characterised by X-ray crystallography and were found to have small internal cavities, helical conformations and multiple intramolecular aromatic interactions. The nucleophilicity of the anion subtly influences the cage shape: Increasing nucleophilicity from SbF6 (1 a) through BF4 (1 b) and O3SCF3 (1 c) to NO3 (1 d) increases the pyramidal distortion at the AgP3 centres, stretching the cage framework (with Ag⋅⋅⋅Ag distances increasing from 5.48 in 1 a to 6.21 A in 1 d) and giving thinner internal cavities. Crystal packing strongly affected the size of the helical twist angle, and no correlation between this parameter and the Ag–Ag distance was observed. When crystalline 1 c was stored in its supernatant for 16 weeks, conversion occured to the isostoichiometric [M2L3]∞ coordination polymer [Ag(dppa)2Ag(dppa)(O3SCF3)2]∞ (1 c′). X-ray crystallography revealed a structure with ten-membered Ag2(dppa)2 rings linked into infinite one-dimensional chains by a third dppa unit. The clear structural relationship between this polymer and the precursor cage 1 c suggests a novel example of ring-opening polymerisation. With dppet, evidence for discrete [M2L3] cages was also found in solution, although 31P NMR spectroscopy suggested some Ag−P bond dissociation. On crystallisation, only the corresponding ring-opened polymeric structures [M2L3]∞ could be obtained. This may be because the greater steric bulk of dppet versus dppa destabilises the cage and favours the ring-opening polymerisation.

A pillared-grid MOF with large pores based on the Cu2(O2CR)4 paddle-wheel

We describe a new interpenetrated pillared-grid structure based on Cu(II) paddle-wheels, 4,4′-biphenyldicarboxylate and 4,4′-bipyridine, with 51% non-framework volume and which retains the same structure on desolvation.

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]- < [C2B9H12]- < [B10Cl10]2- < [B12Cl12]2-. Nevertheless, alkyl chain length dramatically influences the thermal behavior, suggesting that packing inefficiency is the main cause of the existence of room temperature ionic liquids. The salts [C(n)mim][Co(C2B9H11)2] (n = 4, 6, 8, 10, 12 or 14) are liquids at room temperature, presenting strikingly low glass transition temperatures (> or = -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, [C2mim]2[B12Cl12] starts to decompose above 480 degrees C in a dynamic TGA analysis under a dinitrogen atmosphere. Crystal structures of [C2mim][Co(C2B9H11)2] and [C2mim]2[B12Cl12] have been determined. 1H 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.

A novel optically based chemosensor for the detection of blood Na

Abstract The azo dye based chemosensor 2 displays extremely good sensitivity and selectivity for Na+ over other physiologically important alkali and alkali earth metal ions in the 0.3–1.0×10−4 M concentration range as well as being pH independent above pH 3.9. This sensitivity coincides with the Na+ concentration range found in blood. The sensor exhibits almost 110 nm hypsochromic shift in the absorption spectrum upon Na+ detection, with a strong colour change from red to yellow in aqueous solution which is clearly visible to the naked eye even at low concentrations.

Synthesis and reactivity of hexahydropyrroloquinolines

Abstract Formal [4+2] cycloaddition of cyclic enamides with imines derived from aromatic amines gave the 4-arylhexahydropyrroloquinoline skeleton in one step as mixtures of diastereoisomers. Aromatic imines derived from formaldehyde and methylglyoxalate also participated in this chemistry, with the latter favouring formation of the endo -cycloadduct. The cycloadducts derived from methylglyoxalate were unstable and fragmented to give highly substituted quinolines under both neutral and basic conditions. Imines derived from 3-cyanoacrolein also underwent cycloaddition and gave an advanced potential precursor to martinellic acid, albeit with poor diastereoselectivity.