Synthesis of a New Series of Dicationic Ionic Liquids

Abstract

Trabajo presentado en el Iberoamerican Meeting on Ionic Liquids, celebrado en Madrid (España) del 2 al 3 de julio de 2015.Room Temperature Ionic Liquids (RTILs) are a new class of substances that are considered potential substitutes for many traditional organic solvents in reaction processes and others of a different nature.1,2 Because of their low vapour pressures and thermal stability, ILs are strong candidates, at least a priori, for using in certain sustainable processes from an environmental point of view. Most of the current research is conducted using ILs based on pyridinium and imidazolium, which constitute the central nucleus of the cation of the corresponding compound. However, the use of many of these substances has not reached the expected levels. Therefore, the search for new compounds has become one of the research objectives of many groups. In our laboratory, we have synthesised a series of imidazolium-derived di-cationic compounds belonging to the aprotic ionic liquids (AILs) group, using several halides as an anion3. Specifically, we refer to organic 1,ω–bis-(3-metilimidazolium-1-il)- alkane (ω=1-6) chloride, bromide or iodide salts. This communication details the synthesis of the different sets, indicating the most significant physical characteristics and the identification results obtained by 1H-NMR and HRMS. One advantage that ionic liquids present a priori, is that they have lower vapour pressures than the corresponding mono-cationic because of the duplicity of the ion concentration, giving rise, also a priori, to less environmental contamination. Fundamental aspects of the synthesis of seventeen substances (ILs) are presented, indicating some of their physical properties and some aspects of their toxicity. Other questions that could be useful in the field of so-called green-chemistry are also considered in this work, such as biological activity.Peer Reviewe