This journal is c The Royal Society of Chemistry 2013 Chem. Commun., 2013, 49, 2765--2767 2765 Cite this: Chem. Commun., 2013, 49, 2765 Dication magnetic ionic liquids with tuneable heteroanions† Paul Brown, a Craig P. Butts,* a Julian Eastoe,* a Eduardo Padro ´n Herna ´ndez, b Fernando Luis de Araujo Machado b and Rodrigo J. de Oliveira c Dicationic magnetic ionic liquids with heteroanionic anions allow for tunability of physicochemical properties while retaining magnetic susceptibility. Ionic liquids (ILs) are composed solely of cations and anions, imparting tunable properties through chemical structural variation. In addition ILs possess high ion densities, low vapor pressures and high ionic conductivities which have proved beneficial for applications as ‘‘green alternatives’’ to conventional molecular solvents in synthesis, 1,2 separation 3 and electrochemistry. 4,5 ILs have also been designed bearing long alky chain substituents, affording surfactant-like properties. 6–8 Based on IL molecular structure alone, bulk behavior is nearly impossible to predict a priori, however, some general trends have been established; in particular, melting points of ILs depend on ion symmetry (or lack of it), as well as charge densities of the constituent ions. 1,9 The compositions of most ILs reported to date are based on a charge and molar ratio of 1 : 1, so that monocationic and monoanionic species are stoichio- metrically paired. However, dicationic-containing ILs 10,11 have been reported, generally as solids or melting near room temperature, to afford new supramolecular IL architectures with potential applications ranging from lubrication 12 to organic synthesis. 13 Of particular relevance is the report of Chang et al. of ILs where dications are associated with two different anions (heteroanionic), 14 although none of these examples were formally ILs, being solids at room temperature. This emphasizes that the choice of IL anion has a substantial effect on controlling phase/liquid properties, hydrophobicity, electrochemical window, surface activity and, more recently, magnetic responsivity. 15,16 Magnetic ionic liquids 15–18 are especially interesting being ‘molecular’ liquids, as opposed to conventional magnetic fluids (ferrofluids) which comprise colloidal particles (Z10 nm) dispersed in a carrier fluid. 19 Hence, magnetic ionic liquids can be used to formulate nanoparticle-free magnetic emulsions 20 and microemulsions. 21 In addition, ILs with FeCl 4 À anions have proved successful as ‘‘reusable catalysts’’ in Friedel–Crafts reactions, the magnetic properties give advantages over conventional catalysts (AlCl 3 , FeCl 3 and ZnCl 2 ) allowing for easy post use separation/ recovery. 22 Recently, the combined magnetic and catalytic properties of an imidazolium based ionic liquid were applied in esterification of Ac 2 O. 23 Here are described the first dicationic heteroanionic magnetic ILs, which incorporate a common surfactant anion (Aerosol-OT, Fig. 1) and a paramagnetic counterion [FeCl 3 Br]. It is shown, that contrary to previous literature, 14 the heteroanionic dicationic materials give low melting solids whilst still allowing tunability of physico-chemical properties and maintaining magnetic responsivity. This suggests possibilities for other dicationic heteroanionic magnetic ILs with different anions and larger supramolecular architectures (e.g. tri-geminal ionic liquids 24 ) which would bridge the gap between conventional ion-pair ILs and ionic liquid polymers. 22 The synthesis of the homoanionic compounds is straightfor- ward and the generation of a heteroanionic IL is readily achieved Fig. 1 The [C 4 mim] dication and anions studied. a School of Chemistry, University of Bristol, Bristol BS8 1TS, UK. E-mail: Julian.Eastoe@bristol.ac.uk; Fax: +44 (0)117 927 7985; Tel: +44 (0)117 928 9180 b Departamento de Fı ´sica, Universidade Federal de Pernambuco, 50670-901, Recife, Pernambuco, PE, Brazil c Departamento de Quı ´mica, Centro de Cie ˆncias e Tecnologia, Universidade Estadual da Paraı ´ba, 58.429-500 Campina Grande, PB, Brazil † Electronic supplementary information (ESI) available: Synthesis, characterisa- tion and analysis, instrument setup and SQUID data. See DOI: 10.1039/ c3cc00103b Received 5th January 2013, Accepted 21st February 2013 DOI: 10.1039/c3cc00103b www.rsc.org/chemcomm ChemComm COMMUNICATION Published on 22 February 2013. Downloaded by Universidade Federal de Pernanbuco on 13/03/2014 20:22:11. View Article Online View Journal | View Issue