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

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(Cy₃ PO)₂ (H₂ O)₅ ]Br₃ ⋅2 (Cy₃ PO)⋅2 H₂ O ⋅2 EtOH. 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.