Exploring the Vibrational Side of Spin‐Phonon Coupling in Single‐Molecule Magnets via 161Dy Nuclear Resonance Vibrational Spectroscopy

: Synchrotron based Nuclear Resonance Vibrational Spectroscopy (NRVS) using the Mossbauer isotope  161 Dy has been employed for the first time to study the vibrational properties of a single-molecule magnet (SMM) incorporating Dy(III), namely [Dy(Cy 3 PO) 2 (H 2 O) 5 ]Br 3 ·2(Cy 3 PO)·2H 2 O·2EtOH. The experimental partial phonon density of states (pDOS) which includes all vibrational modes involving a displacement of the Dy(III) ion, was reproduced by means of simulations using density functional theory (DFT), enabling the assignment of all intramolecular vibrational modes. This study proves that 161 Dy NRVS is a powerful experimental tool with significant potential to help to clarify the role of phonons in SMMs.