The effect of some amines and alcohols on the organized structure of [bmim][BF4] investigated by 1H NMR spectroscopy

Abstract

The effect exerted by some amines and alcohols on the 1H NMR spectra of 1-butyl-3- methylimidazolium tetrafluoroborate [bmim][BF4] has been studied. This ionic liquid, which is one of the most widely used, is characterized by a high structural order degree, as a consequence of the symmetry and the coordination ability of the anion. In order to have information about the dependence of the detected effects on the alcohol or amine structure, some different primary, secondary and tertiary amines and alcohols have been considered. Furthermore, in the case of amines, their basicity has been also taken into account. Both amines and alcohols induce variation in chemical shifts values and signal multiplicity of imidazolium protons. Collected data show that, among imidazolium protons, the aromatic ones are the most affected by the presence of organic molecule. Cross-correlations among chemical shift values relevant to these protons allow us to explain how 1H NMR spectrum variations depend on probe structural properties.