The objective of this work is to study the effect of the lengthening of the linear alkyl chain of the imidazolium cation on some transport properties. We focused on hydrophobic ionic liquids based on bis(trifluoromethanesulfonyl)imide anion. Among the different properties, we measured at the viscosity and ionic conductivity of four different 1-alkyl-3-methylimidazolium ionic liquid in the temperature range between 293 and 333K. Thus, Electrochemical windows of these ionic liquids and the diffusion coefficient of ferrocenemethanol (FcMeOH) in the four ionic liquids were studied using cyclic voltammetry at 298K. The FcMeOH diffusion coefficient was found to be higher in shorter alkyl chain ionic liquids.