Electrochemical study of dialcarb "distillable" room-temperature ionic liquids

Electrode-dependent potential windows (see picture, GC=glassy carbon) are determined for five dialkylammonium carbamate (dialcarb) room-temperature ionic liquids in a systematic study of their physical and electrochemical properties. The viscosity and conductivity of the dialcarb ionic liquids, which are "distillable" at low temperature, are comparable to those of some conventional room-temperature ionic liquids. The physical and electrochemical properties of five "distillable" room-temperature ionic liquids from the dialcarb family (dialkylammonium carbamates formed from CO(2) and dialkyl amines) are systematically investigated. In particular dimethyl (DIMCARB), diethyl (DIECARB), dipropyl (DIPCARB), methylethyl (MEETCARB), and methylpropyl (MEPRCARB) carbamate ionic liquids are studied. The temperature dependence of the viscosity and conductivity of MEETCARB exhibit an Arrhenius-type relationship. Except for DIPCARB, which has too high a resistance, a reference potential scale is available by using the IUPAC recommended redox system, that is the cobalticenium/cobaltocene (Cc(+)/Cc) process, which exhibits an ideal reversible voltammetric response. Oxidation of decamethylferrocene, but not ferrocene, also is ideal in DIMCARB, DIECARB, MEETCARB, and MEPRCARB. The magnitudes of the potential windows of the electrochemically viable dialcarbs are investigated and follow the order of glassy carbon>Au>Pt>Hg. Diffusion coefficients of Cc(+), DmFc, and double-layer capacitance values are compared in each dialcarb. Despite the considerable viscosity of the dialcarbs, steady-state voltammetric behavior is achieved at a rotating disk electrode for rotation rates of 1000 rpm or higher.