Grant A. Broker

Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation

A series of hydrophilic and hydrophobic 1-alkyl-3-methylimidazolium room temperature ionic liquids (RTILs) have been prepared and characterized to determine how water content, density, viscosity, surface tension, melting point, and thermal stability are affected by changes in alkyl chain length and anion. In the series of RTILs studied here, the choice of anion determines water miscibility and has the most dramatic effect on the properties. Hydrophilic anions (e.g., chloride and iodide) produce ionic liquids that are miscible in any proportion with water but, upon the removal of some water from the solution, illustrate how sensitive the physical properties are to a change in water content. In comparison, for ionic liquids containing more hydrophobic anions (e.g., PF6− and N(SO2CF3)2−), the removal of water has a smaller affect on the resulting properties. For a series of 1-alkyl-3-methylimidazolium cations, increasing the alkyl chain length from butyl to hexyl to octyl increases the hydrophobicity and the viscosities of the ionic liquids increase, whereas densities and surface tension values decrease. Thermal analyses indicate high temperatures are attainable prior to decomposition and DSC studies reveal a glass transition for several samples. ILs incorporating PF6− have been used in liquid/liquid partitioning of organic molecules from water and the results for two of these are also discussed here. On a cautionary note, the chemistry of the individual cations and anions of the ILs should not be overlooked as, in the case of certain conditions for PF6− ILs, contact with an aqueous phase may result in slow hydrolysis of the PF6− with the concomitant release of HF and other species.

Mercury(ii) partitioning from aqueous solutions with a new, hydrophobic ethylene-glycol functionalized bis-imidazolium ionic liquidThis work was presented at the Green Solvents for Catalysis Meeting held in Bruchsal, Germany, 13–16th October 2002.

A room temperature ionic liquid containing a bis-imidazolium cation incorporating a short ethylene-glycol spacer, 1,1′-[1,2-ethanediylbis(oxy-1,2-ethanediyl)] bis[3-methyl-1H-imidazolium-1-yl]bis(trifluoromethanesulfonyl)imide, has been prepared from the corresponding chloride salt, and the X-ray crystal structure of the low-melting hexafluorophosphate salt has been determined. The crystal structure reveals the ether linkage to be quite flexible and to participate in strong C2–H⋯O hydrogen bonds leading to asymmetry. The crystal structure of the bis-imidazolium salt incorporating a decyl-spacer, 1,1′-[1,10-decyl]bis[3-methyl-1H-imidazolium-1-yl] hexafluorophosphate, has also been determined and displays an all-trans (symmetric) conformation except at the beta carbon positions where a characteristic kink is observed. Introducing the ethylene-glycol functionality dramatically increases the distribution ratio of mercury ions, but not caesium, from aqueous solution to the hydrophobic ionic liquid, and from basic solution. This is the first example of pH dependent partitioning and stripping of mercury from ionic liquid/aqueous two-phase systems. The crystal structure of the related mercury(II) carbene complex, obtained from the reaction of mercury(II) acetate with 1,1′-[oxybis(2,1-ethanediyloxy-2,1-ethanediyl)]bis[3-methyl-1H-imidazolium-1-yl] tosylate, containing a three-ether spacer, in acetonitrile, reveals the possibility of a carbene extraction mechanism.

Synthesis and characterization of mono- and bis-(tetraalkylmalonamide)uranium(VI) complexes

The complex [UO 2 (NO 3 ) 2 (TMMA)] (TMMA= N , N , N ′, N ′-tetramethylmalonamide) was structurally characterized by single-crystal X-ray diffraction. The complex consists of two bidentate nitrate ions and one bidentate TMMA ligand coordinated to the UO 2 2+ ion. The complex [UO 2 (THMA) 2 ] 2+ (THMA= N , N , N ′, N ′-tetrahexylmalonamide) was prepared as the BF 4 − salt; this material tended to form an oil. However, [UO 2 (TMMA) 2 ](OTf) 2 (OTf=triflate) was isolated as a crystalline solid. Comparison of the Fourier transform infrared spectra of these complexes to the spectra of complexes formed in liquid–liquid extraction systems supports the hypothesis that complexes of the type [UO 2 (NO 3 ) 2 L] and [UO 2 L 2 ](NO 3 ) 2 (L=diamide extractant) form in the extraction systems.

Synthesis of chiral trans-anti-trans-isomers of dicyclohexano-18-crown-6 via an enzymatic reaction and the solid-state structure of one enantiomer

Abstract Chiral trans-anti-trans-dicyclohexano-18-crown-6 isomers are synthesized via a lipase-catalyzed reaction. The solid-state structure of the (S)-enantiomer is determined and compared with those reported for 18-crown-6 and trans-syn-trans-dicyclohexano-18-crown-6.

Synthesis and transformations of some new 2,4-bismethylene-1,3-ditelluretanes

A novel four-membered 1,3-ditelluretane dialdehyde 8/9 was synthesized from trimethylsilylethynyl tellurolate. The dialdehyde was transformed into extended tetrathiafulvalenes (14 and 15). These are the first examples of ditelluretane spaced TTF derivatives.

Polar, non-coordinating ionic liquids as solvents for the alternating copolymerization of styrene and CO catalyzed by cationic palladium catalysts

The palladium-catalyzed copolymerization of styrene and CO in an ionic liquid solvent, 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide, gave improved yields and increased molecular weights compared to polymerizations run in methanol.

Self-assembly of freebase- and metallated-tetrapyridylporphyrins to modified gold surfaces

Freebase- and metallated-tetrapyridylporphyrins self-organize through multiple hydrogen bonding to carboxylic acid terminated self-assembled monolayers on gold surfaces, thereby producing surfaces with two additional functional sites, the porphyrin cavity and the terminal pyridyl groups.

Bis[N-(2-hy­droxy­eth­yl)-N-propyl­dithio­carbamato-κ2S,S′]bis­(4-{[(pyridin-4-yl­methyl­idene)hydrazinyl­idene]meth­yl}pyridine-κN1)cadmium

The complete molecule of the title compound, [Cd(C6H12NOS2)2(C12H10N4)2], is generated by crystallographic inversion symmetry. The distorted octahedral trans-N2S4 donor set for the Cd2+ ion is defined by two symmetrically S,S′-chelating dithiocarbamate anions and two pyridine N atoms derived from two monodentate 4-pyridinealdazine (or 4-{[(pyridin-4-ylmethylidene)hydrazinylidene}methyl]pyridine) molecules [dihedral angle between the aromatic rings = 17.33 (8)°]. In the crystal, molecules are connected into a supramolecular chain via O—H⋯N hydrogen bonds involving the 4-pyridinealdazine N atoms not involved in coordination to cadmium. Weak C—H⋯O and C—H⋯N links consolidate the packing.

Green chemistry and lanthanide-based crystal engineering

Abstract The concept of ‘Green Chemistry’ has received much recent attention due to increased environmental regulations and concerns. This concept is currently being applied to industrial processes as an attempt to help reduce hazardous discharges into the environment. The opportunities to practice green chemistry, however, are abundant in modern science and technology. Here we discuss the concepts of green chemistry as related to crystal engineering, a promising field that may lead to more environmentally-friendly processes and help aid in environmental clean-up by the design of functional solid state materials. Lanthanides with their rich stereochemistry and abundant nature are currently underutilized in crystal engineering development.

(2-Hydroxy­ethyl)(prop­yl)aza­nium 2-[(2-carboxy­phen­yl)disulfan­yl]benzoate monohydrate

With the exception of the terminal hydroxy group [N—C—C—O = 53.8 (5)°], the cation of the title salt hydrate, C5H14NO+·C14H9O4S2 −.H2O, is a straight chain. A twisted conformation is found for the anion [C—S—S—C = −87.44 (16)°]. In the crystal, the anions self-assemble into a helical supramolecular chain via charge-assisted O—H⋯Oc hydrogen bonds. These chains are connected into a three-dimensional network via N—H⋯Oc, N—H⋯Ow, Oh—H⋯Ocb, and Ow—H⋯Oc hydrogen-bonding interactions (c = carboxylate, w = water, h = hydroxy and cb = carbonyl).