Synthesis, characterisation and properties of ferrocenylalkylimidazolium salts

New ferrocenylalkylimidazolium salts [Fc(CH2)n(C3H3N2)R]X− were synthesised through the incorporation of green chemistry principles of atom economy and when feasible under solvent-free conditions. The products comprise a series of salts all characterised by the ferrocenyl moiety with variations in the length of the linker alkyl chain (n), the size of the imidazolium alkyl substituent (R) or the electronic nature of the counter-ion (X−). The dependence of the physical and electronic properties of the salts on the three main structural variants was studied. It was found that variation in the steric size of the R group has the most profound influence on the melting points of the ionic liquids. The compounds were fully characterised by IR, 1H and 13C NMR, MS and melting point determinations.