A physicochemical investigation of ionic liquid mixtures.

Ionic liquids have earned the reputation of being 'designer solvents' due to the wide range of accessible properties and the degree of fine-tuning afforded by varying the constituent ions. Mixtures of ionic liquids offer the opportunity for further fine-tuning of properties. A broad selection of common ionic liquid cations and anions are employed to create a sample of binary and reciprocal binary ionic liquid mixtures, which are analysed and described in this paper. Physical properties such as the conductivity, viscosity, density and phase behaviour (glass transition temperatures) are examined. In addition, thermal stabilities of the mixtures are evaluated. The physical properties examined for these formulations are found to generally adhere remarkably closely to ideal mixing laws, with a few consistent exceptions, allowing for the facile prediction and control of properties of ionic liquid mixtures.

A step towards the a priori design of ionic liquids.

A range of methods for the computational prediction of experimentally derived α and ß Kamlet-Taft parameters, indicators of hydrogen bond (H-bond) acidity and basicity for ionic liquids (ILs) have been explored. Most usefully, a good correlation has been established between several simple and easily computed quantities which allow for a "quick bench-top" evaluation. More accurate, but also more sophisticated methods employing TD-DFT calculations involving the Kamlet-Taft dyes have been examined and evaluated. Importantly, these techniques open up the opportunity for pre-screening and a priori prediction of properties for ILs not yet synthesised. A key fundamental insight into IL H-bonds has been the determination of an estimate for the energy associated with replacing both neutral molecules in a H-bond with ionic molecules, thus forming the "doubly ionic" H-bond found in ILs.

Mixtures of ionic liquids.

Simple ionic liquids have long been held to be designer solvents, based upon the ability to independently vary their cations and anions. The formation of mixtures of ionic liquids increases this synthetic flexibility. We review the available literature of these ionic liquid mixtures to identify how their properties change and the possibility for their application.

Self-assembly in the electrical double layer of ionic liquids.

We have studied the structure of two ionic liquids confined between negatively charged mica sheets. Both liquids exhibit interfacial layering, however the repeat distance is dramatically different for the two liquids. Our results suggest a transition from alternating cation-anion monolayers to tail-to-tail cation bilayers when the length of the cation hydrocarbon chain is increased.

Understanding siloxane functionalised ionic liquids.

In this paper we use ab initio theoretical methods in combination with experimental studies to investigate ion-pairs of the ionic liquid (IL) 1-methyl-3-pentamethyldisiloxymethylimidazolium chloride [(SiOSi)C(1)C(1)im]Cl, in order to deepen our understanding of the effects of functionalisation on an IL. In addition, we focus on the effect of the siloxy group on the viscosity. We establish that the ion-pairing energies of [(SiOSi)C(1)C(1)im]Cl are similar to those of 1-butyl-3-methylimidazolium chloride [C(4)C(1)im]Cl, because the anion interacts primarily with the imidazolium ring. A large range of ion-pair structural configurations is possible with different anion positions and chain orientations, contributing to a significant entropy. A H-bonded network forms, however the siloxy chain can shield the Cl(-) or key C-H sites thus introducing defects. Despite a significant increase in mass relative to [C(4)C(1)im](+), the combined barriers to rotation within the substituent chain are substantially reduced in [(SiOSi)C(1)C(1)im](+), this is primarily due to the flexibility of the siloxane linkage, and free rotation of the Si-Me methyl groups. The most important effect is a coupling of rotational motions within the chain which leads to dynamic inter-conversion of cation conformers, and facilitates movement of the anion around the cation, these will contribute to enhanced transport properties and a reduced viscosity. In addition, a longer charge arm is expected to enhance rotational and rotational-translational coupling in electric fields. Thus, for [(SiOSi)C(1)C(1)im]Cl ion-pair association is very similar to that of [C(4)C(1)im]Cl, but "dynamic" properties relating to torsional motion, a dynamic H-bonded network, and cation response to an external electric field are enhanced.

Intermediate spin ground state of an isosceles triangular [Mn(II)(3)] complex.

[{Mn(tmeda)}(3){GeSe(3)(OMe)}(2)] (), synthesized by the reaction of [K(4)(H(2)O)(3)][Ge(2)Se(6)] with MnCl(2).4H(2)O in MeOH-tmeda (tmeda = N,N,N',N'-tetramethyl-1,2-diaminoethane), exhibits an isosceles triangular arrangement of Mn(2+) ions that are antiferromagnetically coupled with an S = 3/2 ground state.

Synthesis and properties of the tetranuclear palladium chalcogenolato-acetato complex [Pd(SePh)(OOCCH3)]4 with Pd-Pd bonding: an experimental and theoretical study.

The first tetranuclear palladium selenophenolate complex has been synthesized by reaction of palladium acetate with (PhSe)(3)Sn-(CH(2))(4)-Sn(SePh)(3) () in dichloromethane. represents a rectangular arrangement of the four Pd atoms bridged by four mu-bridging SePh and OAc groups each and is thermolyzed into a novel phase Pd(10)Se(7). The alternating distribution of acetate or selenophenolate bridges over the PdPd edges, that allows for the formation of two Pd-Pd bonds, was rationalized by quantum chemical investigations.