Melting point, of ionic liquids

The cations in ionic liquids are generally bulky monovalent organics. The typical cations of ionic liquids, not including the familiar alkylammonium and alkylphosphonium ions, are shown in Fig. 2. It is primarily the cations, which account for the low melting points of ionic liquids. The dialkylimidazolium ions, such as 1-butyl-3-methyl imidazolium [BMIM], have been widely investigated because low-melting ionic liquids can be made readily from such cations and because of their thermal and chemical stability. 

Characteristics which contribute to the low melting points of ionic liquids are large cations and anions with low symmetry and delocalised charge [62], often featuring an aromatic or cyclic structure and long alkyl chains. Many ionic liquids have negligible vapour pressure [63], and are non-flammable [64, 65], They can also be... 

Alternative approaches to the study of melting points of ionic liquids include molecular dynamics simulations such as that conducted by Alavi and Thompson [35], Here simulations of [C2mim][PF6] over a wide temperature range, which... 

Perhaps the most important property of an ionic liquid is whether it is a liquid or not in the temperature range at which you are operating. While it is very well known as to which molecular properties influence the melting points of ionic liquids, their accurate prediction is stiU not possible. One reason for this is that many ionic hquids are glass-forming materials that do not display a well-defined melting point. 

Preiss, U., Bulut, S. and Krossing, I., In silico prediction of the melting points of ionic liquids from thermodynamic considerations a case study on 67 salts with a melting point range of 337°C, J. Phys. Chem. B 114,11133-11140 (2010). 

Is the liquid or the solid phase responsible for the low-melting points of ionic liquids Alkyl-chain-length dependence of thermodynamic properties of [C mim][NTf2]. 

Torrecilla, J.S., Rodriguez, R, Bravo, J.L., Rothenberg, G., Seddon, K.R. and Lopez-Martin, L, Optimising an artificial neural network for predicting the melting point of ionic liquids, Phys. Chem. Chem. Phys. 10 (38), 5826-5831 (2008). 

Lazzus, J.A., A group contribution method to predict the melting point of ionic liquids. 

Yan, F.Y, Xia, S.Q., Wang, Q., Yang, Z. and Ma, P.S., Predicting the melting points of ionic liquids by the quantitative structure property relationship method using a topological index, J. Chem. Thermodyn. 62,196-200 (2013). 

Table 2. Molecular structure and melting point of ionic liquid lubricants.

---