A weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tris(pentafluoroethyl)- trifluorophosphate ([Emim]+[FAP]−), is investigated by DFT method at B3LYP/6-31+G(d, p) level. Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of hydrogen bonds. Further investigation through Natural Bond Orbital (NBO) analysis provided insight into the origin for weaker ion pair interactions. Harmonic vibrations of the ion pair were calculated and compared with the experimental Raman and infrared spectra. Assignments and frequency shifts are discussed in light of the inter-ionic interactions.