Conductometric study of ionic liquids in the presence of N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE) Schiff base in acetonitrile solutions at 298.15 K

In recent years, Schiff bases and their metal complexes in the presence of ionic liquids (ILs) have been used in synthesis of various chemical compounds. To better understanding of ionic liquid influence on these processes, it is required to obtain information about the ion association behavior of the ionic liquids. Therefore, in this work, the molar conductivities of the ILs [RMIm]X (R= propyl, pentyl, and hexyl; X= Br− and Cl−) in different concentrations of N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE) Schiff base + acetonitrile solutions were determined at 298.15 K. The obtained conductivity data were analyzed by low concentration Chemical Model (lcCM) conductivity equation to calculate the limiting molar conductivities (Λ0) and ion association constants (KA). The results show that BPIE, alkyl chain length of cation, and anion type have effect on the ionic association process of the ILs. The Λ0 and KA values decrease as the Schiff base concentration, alkyl chain length of cation, and anion size increase in the solution. The association constants were also used to calculate the standard Gibbs energy (ΔG0A) of ion-pairing association. The resulted ΔG0A values are negative and become more negative as the alkyl chain length of the cation and the size of anion increase. The large negative values of the standard Gibbs energy obtained for [HMIm]Br indicates the more spontaneity and the more feasibility of the association process for this ionic liquid.