Vibrational signatures of anionic cyano groups in imidazolium ionic liquids

•A Fermi resonance of a combination band and a CN stretching normal mode is found in the dicyanamide anion.•Ab initio molecular dynamics (AIMD) simulations allow the determination of spectra of individual ions.•The combination of experimental spectroscopy and advanced AIMD simulations is a very promising approach to gain new physical insights.