Measurement and Analysis of Vibronic Coupling in Two Dysprosium(III) Complexes of Opposite Magnetic Anisotropy

The loss of magnetic memory in single-molecule magnets (SMMs) is caused by the coupling of molecular vibrations to spin states, which plays a significant role in magnetic relaxation processes. Gaining direct evidence of vibronic coupling using experimental techniques is critical to understanding and controlling this phenomenon. Most studies focus on assessing the spin-phonon coupling in SMMs to help control this relaxation; herein we gain insight by comparing the SMM [Dy(OPCy₃)₂(H₂O)₅][CF₃SO₃]₃.2(OPCy₃) to the non-SMM [Dy{N(SiMe₃)₂}₃] through collection of far-infrared magnetospectroscopy (FIRMS) spectra and validation with ab initio calculations. Single-crystal measurements display a prominent feature in the spectra at 340 cm^-1, corresponding to an electronic excitation which varies depending on the direction of external magnetic field applied. These findings demonstrate the complicated effect of magnetic anisotropy on the vibronic coupling in SMMs and demonstrate the power of FIRMS to study these effects.