Fatty acid and alcohol based low melting mixtures: The role of intermolecular interactions by DFT and infrared spectroscopy

DFT calculations and infrared spectroscopy are exploited in the present work to study two low melting mixtures obtained by mixing tetrabultylammonium trifluoromethanesulfonate (TBATFO) with two fatty compounds, 1-octanol (C8OH) and octanoic acid (C7COOH). This choice allows the investigation of the role of the TFO anion, that has an asymmetric structure with two potential Hydrogen Bond Acceptor (HBA) groups, sulfonate (SO3−) and trifluoromethyl (CF3−) groups, when mixed with two organic compounds having an alkyl chain of similar length but with Hydrogen Bond Donor (HBD) groups of different force, hydroxyl and carboxylic groups. The obtained results and topological properties indicate that generally the acid promotes a more efficient hydrogen bond with the TFFO anion in comparison with the octanol. Moreover, the long and amphiphilic alkyl chains of fatty alcohols and acids allow to shed light on the role of the van der Waals interactions between alkyl tails, which are found to be fundamental, together with the hydrogen bonding between the components, in determining the properties of this kind of systems.