A thermochromic magnetic ionic liquid containing a cationic iron(III) Schiff-base complex has been developed, whose color and magnetic moment change with temperature because of spin crossover in the liquid state. This spin-crossover behavior closely resembles that of a solid having the same cation.

A series of salts comprising cationic manganese(III)-salen complexes and the Tf 2 N anion has been prepared (salen = N,N′-bis(salicylideneaminato)ethylene, Tf 2 N = bis(trifluoromethanesulfonyl)amide) to investigate the effects of axial ligands and substituents on their thermal properties.[Mn(salen)L 2 ][Tf 2 N] (L = H 2 O, Pyridine) and their 5-butoxysalen analogues undergo thermal desorption of the axial ligands, followed by decomposition above 250°C. The pyridine complexes exhibit two-step ligand desorption, corresponding to the formation of a dimer and later, desorption from the dimer. Complexes with L = 3-butylpyridine and N-butylimidazole melt at 97.6°C and 132.7°C, respectively, before ligand desorption. Crystal structures of these and related complexes have been determined. [Mn(salen)(3,3′-bipyridine)][Tf 2 N] is a coordination polymer with higher thermal stability.

bis(acetylacetone)ethylenediamine, Tf 2 N = bis(trifluoromethanesulfonyl)amide) were prepared. 1 is a liquid at room temperature and exhibits a glass transition at −12 °C, whereas 2 is a solid at room temperature with a melting point of 74.6 °C and glass transition temperature of −15 °C upon cooling from the melt. These salts are red-brown diamagnetic materials that are stable against air and water; these properties differ from those of the corresponding iron(III) salt. Desorption of the axial ligands of 1 and 2 occurs at 180 and 207 °C, respectively.

In recent years, solvate and protic ionic liquids (ILs) have attracted much attention. We synthesized both types of ILs from alkyl aza-crown ethers (L = N-propyl-1-aza-15-crown-5 (L) and N-CFCH-1-aza-15-crown-5 (L)). The solvate ILs [ML][TfN] (M = Na, K) were solids (T = 58-68 °C), whereas the solvate ILs [ML][TfN] (M = Li, Ag) and protic ILs [HL][TfN] were liquids with low glass transition temperatures. The ILs containing Na ions were more crystalline and exhibited higher melting points than the other ILs. The decomposition temperatures of the protic ILs were higher than those of the solvate ILs. A protic IL with a paramagnetic anion, [HL][FeCl] (T = 70.5 °C), was also synthesized and its crystal structure was determined. The solvate ILs [NaL][X] (X = Cl, CFCO, TsO, PhSO) exhibited a lower critical solution temperature (LCST)-type behavior in water. The effects of salt addition on the LCST of L were also investigated. The LCST of these ILs generally increased with increasing hydrophilicity or basicity of the counter anion. This tendency, which is nearly opposite to that of ILs with quaternary onium cations, is ascribed to the amphiphilic nature of the cation. The corresponding protic ILs did not exhibit LCST behavior.