Physical trends and structural features in organic salts of the thiocyanate anion

A new series of ionic liquids based on the thiocyanate anion has been prepared. Incorporation of this anion with an imidazolium, tetraalkylammonium or pyrrolidinium cation produces ionic liquids with advantageously low melting points and good thermal stability. The low temperature phase behaviour of the salts has been investigated using differential scanning calorimetry and multiple solid phases have been observed. The electrochemical windows of representative imidazolium and pyrrolidinium species have been investigated by cyclic voltammetry and determined to be 2.4 and 3.5 V, respectively. In addition, the solid-state structure of N,N-dimethylpyrrolidinium thiocyanate has been determined by X-ray crystallography. This is the first reported structure of a pyrrolidinium thiocyanate species and shows a layered structure with linear thiocyanate groups having bond lengths comparable to those observed in similar SCN−-containing species.

Parallel developments in aprotic and protic ionic liquids : physical chemistry and applications

This Account covers research dating from the early 1960s in the field of low-melting molten salts and hydrates,which has recently become popular under the rubric of “ionic liquids”. It covers understanding gained in the principal author’s laboratories (initially in Australia, but mostly in the U.S.A.) from spectroscopic, dynamic, and thermodynamic studies and includes recent applications of this understanding in the fields of energy conversion and biopreservation. Both protic and aprotic varieties of ionic liquids are included, but recent studies have focused on the protic class because of the special applications made possible by the highly variable proton activities available in these liquids.