Supramolecular Interactions Modulate Raman Relaxation in D_5h Symmetric Dy(III) Single-Molecule Magnets Opening the...

Dysprosium-based single-molecule magnets (SMMs) exhibit large magnetic anisotropy and coercive fields, offering the potential to support information storage at the molecular level. Owing to the molecular nature of SMMs, supramolecular interactions are usually perceived as weak and negligible in shaping their magnetic hysteresis. Here we designed a series of compounds to show that supramolecular interactions instead play a key role in governing the hysteresis loops of SMMs via controlling the efficiency of Raman relaxation. We chose the pentagonal-bipyramidal (PB) family of Dy(III) SMMs that has a cationic complex with the common formulas of [Dy(L)₂(py)₅]⁺ and a fixed anion of [BPh₄]^-. Here we vary only the peripheral parts of the axial ligands with disparate strength of supramolecular interactions. For HL = cyclohexylmethanol (PB-hx), there is no intramolecular C-H···π interactions, while for one phenyl ring based HL = benzyl alcohol (PB-bz) or (S)-(-)-1-phenylethanol (PB-pe), there are intermediate supramolecular interactions, and the largest HL = 9-anthracenemethanol (PB-an) does give the strongest C-H···π interactions. Magnetic, spectroscopic, and ab initio spin dynamics simulation studies provide solid evidence that these supramolecular interactions directly participate in the mitigation of the two-phonon Raman process, supporting the observed gradual enhancement of blocking temperature (T_B^H at the field sweep rate of 200 Oe/s) of 38, 42, and 46 K for PB-hx, PB-bz, and PB-pe and finally 50 K for PB-an, the highest value ever reported for this class of compounds. Our study provides a new and promising paradigm to mitigate Raman relaxation and pave the way to novel high-temperature SMMs.