Supramolecular Interactions Modulate Raman Relaxation in D5h Symmetric Dy(III) Single-Molecule Magnets Opening the Magnetic Hysteresis up to 50 K

Dysprosium-based single-molecule magnets (SMMs) exhibit large values of magnetic anisotropy and large coercive fields, offering the potential to support magnetic information storage at the molecular level. Owning to the molecular nature of SMMs, supramolecular interactions are usually perceived as weak and negligible in shaping their magnetic hysteresis loop. Here, we designed a series of compounds to show that supramolecular interactions instead play a key role in governing the hysteresis loop of SMMs via controlling the efficiency of Raman relaxation. We chose the D5h symmetric or pentagonal-bipyramidal (PB) family of Dy(III) SMMs which has a cationic complex with the common formulae of [Dy(L)2(py)5]+ and a fixed anion of [BPh4]-. Here we vary only the peripheral parts of the axial L 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 two-phonon Raman relaxation process, supporting the observed gradual enhancement of the blocking temperature (TBH at the field sweep rate of 200 Oe/s) of 38 K, 42 K, and 46 K for PB-hx, PB-bz, PB-pe, and finally to 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 SMMs with enhanced magnetic blocking temperature.