Synthesis, NMR, vibrational spectroscopy, thermal and DFT studies of new DABCO hexafluorophosphate based ionic liquid

•A new [C8DABCO+][PF6−] based ionic liquid.•The IL was characterized by using NMR and FTIR and Raman spectroscopies.•The thermal property of IL was investigated by means TGA and DTA measurements.•B3LYP/6–31G* calculations support the high solvation energy value of IL.•DABCO structure plays a very important role in the properties of IL. In this paper, a new ionic liquid; [C8DABCO+][PF6−] was prepared, its structure was well confirmed by 1H, 13C, 19F and 31P–NMR spectroscopies. Besides, thermal behaviour has been discussed through TGA and DTA in the temperature range from [-80 to 200 °C] and [25 to 700 °C] respectively. Theoretical studies were performed by DFT method to investigate the structural, electronic and topological properties. B3LYP/6–31G* calculations support the high solvation energy value of IL in aqueous solution (ΔGc= -122.9 kJ/mol) and it probably explain the high dipole moment value, the volume expansion in this medium (7.3 Å3) and also because the cation-anion interactions still remain in solution. Seven interactions were predicted by AIM calculations but only two cation-anion interactions have short distances. NBO studies reveal that IL is more stable in solution probably due to its higher solvation energy. The DOS spectrum in aqueous solution shows clearly that the orbitals belonging to the atoms of cage-like DABCO structure participle in both HOMO and LUMO and, hence, will confirm that DABCO is engaged in halogen interactions, as suggested from NBO analyses. These studies show that DABCO structure participates in the properties of [C8DABCO+][PF6−]. Complete assignments of IR and Raman spectra were reported. [Display omitted]