Mixtures of choline chloride and tetrabutylammonium bromide with imidazole as examples of deep eutectic solvents: their structure by theoretical and experimental investigation

Imidazole based eutectic solvents have been recently proposed as novel solvents and have been synthetized and characterized by different experimental techniques. We studied the structure of two deep eutectic solvents (DESs) based on imidazole and two organic salts (tetrabutylammonium bromide, TBABr, and choline chloride, ChCl). We focused our attention on the microscopic distribution of their components in the liquids by a study of Infrared and Raman spectroscopy and X-ray diffraction. The vibrational spectra of the eutectic mixtures have been analysed with the aim to characterized the nature of the interactions between anions, cations and imidazole. X-ray diffraction pattern has been interpreted on the light of the intermolecular contacts. Vibrational spectra and diffraction data have been compared with the results of computational studies obtained for both the DESs by molecular dynamics and quantum chemistry calculations.