Tim Hochdörffer, Juliusz A. Wolny, Andreas Omlor, Lena Scherthan, Hendrik Auerbach, Christina S. Müller, Hans-Christian Wille, Ilya Sergeev, Volker Schünemann

• Within this work, we report the results of nuclear inelastic scattering experiments of the low-spin phase of the iron(II) mononuclear SCO complex Fe[HBpz3]2 and density functional theory based calculations performed on a model molecule of the complex. We show that the calculated partial density of vibrational states based on the structure of a single iron(II) center which is linked by three pyrazole rings to borat is in good accordance with the experimentally obtained 57Fe-pDOS and assign the molecular vibrations to the prominent optical phonons.