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

Bad vibrations? $^{161}$Dy nuclear resonance vibrational spectroscopy gives direct experimental access to the partial phonon density of states which includes all vibrational modes involving a displacement of the Dy$^{III}$ ion. In combination with density functional theory, an assignment to all intramolecular vibrational modes is possible, paving an ideal path to help to clarify the role of phonons in single-molecule magnets.

Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS) using the Mössbauer 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)⋅2 H$_{2}$O ⋅2 EtOH. The experimental partial phonon density of states (pDOS), which includes all vibrational modes involving a displacement of the DyIII 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.