Ferrocene based ionic liquid: synthesis, structure, transport properties and mechanism of thermal degradation

Abstract

Doping with transition metals is a promising way to expand the industrial applications of ionic liquids (ILs). This study reports the synthesis, structure and physicochemical properties of a novel butyl-dimethyl-(ferrocenylmethyl)ammonium bis(trifluoromethanesulfonyl)imide ([BDFA][NTf2]) IL. The thermo-gravimetric analysis combined with mass spectrometry of evolved gases demonstrated the high thermal stability of [BDFA][NTf2] up to 500 K. The thermal degradation of [BDFA][NTf2] at higher temperatures is a multi-step process accompanied by the cation destruction through the Hofmann elimination reaction and the subsequent transformations, such as fragmentation of the products of thermal degradation of the [NTf2]-anion and the direct interaction between these products. The glass transition and melting temperatures of [BDFA][NTf2] measured by the differential scanning calorimetry are 229 and 320 K, respectively. The electrical conductivities and densities of binary mixtures of [BDFA][NTf2] with acetonitrile (AN) were measured in the temperature range of 293 – 348 K at atmospheric pressure. The isobaric thermal expansion coefficients were calculated from the experimental data. The conductivity – temperature dependences were analyzed using the Arrhenius and Vogel-Fulcher-Tammann equations. The activation energy of ion transport and limiting conductivity increased with the IL mole fraction in AN.