New insights into the relationship between ion-pair binding energy and thermodynamic and transport properties of ionic liquids

To aid in the design of novel task-specific ionic liquids (ILs), this study investigates the relationship between trends in ion-pair binding energy (IPBE) and trends in thermodynamic and transport properties of ILs. Unlike previous studies, this study considers the two major components of the IPBE, namely, the electrostatic and dispersion interactions, and suggests how these components relate to melting point and transport properties such as conductivity and viscosity. A range of N-methyl-N-alkylpyrrolidinium and N-methyl N-alkylimidazolium-based salts paired with Br-, BF4-, PF6-, N(CN)2-, N(SO2CF3)2- (also known as NTf2 -), mesylate,and tosylate anions were studied. It was found that the ratio of total IPBE to its dispersion component correlates well with melting point, whereas the dispersion component of the IPBE correlates well with conductivity and viscosity.