In this review, the roles of room temperature ionic liquids (RTILs) and RTIL based solvent systems as proposed alternatives for conventional organic electrolyte solutions are described. Ionic liquids are introduced as well as the relevant properties for their use in electrochemistry (reduction of ohmic losses), such as diffusive molecular motion and ionic conductivity. We have restricted ourselves to provide a survey on the latest, most representative developments and progress made in the use of ionic liquids as electrolytes, in particular achieved by the cyclic voltammetry technique. Thus, the present review comprises literature from 2015 onward covering the different aspects of RTILs, from the knowledge of these media to the use of their properties for electrochemical processes. Out of the scope of this review are heat transfer applications, medical or biological applications, and multiphasic reactions.

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The reaction of copper(II) nitrate hydrate with sodium 2‐[2‐(2,4‐dioxopentan‐3‐ylidene)hydrazinyl]terephthalate (Na2HL1) in the absence or presence of imidazole (im) leads to the new complexes [(H2O)Cu0.5{(μ‐L1‐1κO:2κ3N,O′,O″)Cu(H2O)2}]2 (1) and [Cu(im)(μ‐HL1‐1κO:2κ3N,O,O′)]2 (2), respectively, whereas the 1D coordination polymer [Cu2(H2O)2(μ‐H2L2‐1κ3N,O,O′:2κO″)(μ‐L2‐1κ3N,O,O′:2κ2N′,O″)]n (3) is obtained from Cu(NO3)2·2.5H2O and sodium 2‐[2‐(4,4‐dimethyl‐2,6‐dioxocyclohexylidene)hydrazinyl]terephthalate (Na2HL2). All of the compounds were characterized by ESI‐MS, IR spectroscopy, elemental analysis and X‐ray diffraction analysis. Di‐ or tri‐deprotonated ligands display different coordination modes and lead to distinct nuclearities of the CuII complexes depending on the conditions used for the syntheses. Complexes 1–3 were successfully tested as dual‐role catalysts for cyclohexane oxidation under acid‐free conditions in the ionic liquid [1‐butyl‐3‐methylimidazolium tetrafluoroborate, (bmim)(BF4)] as well as in acetonitrile. The application of the ionic liquid (IL) increased the product yield and turnover number and decreased the reaction time, in comparison with those for the use of the conventional acetonitrile solvent. Easy recycling of the catalyst, with preservation of almost the initial activity and selectivity, was also achieved by using the IL medium.

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