A hydroxyl-extended 1D dysprosium chain with two well-separated magnetic relaxation processes

A 1D dysprosium chain {[Dy(CH₃OH)Cl₂(tpy)]·CH₃OH}_n (Htpy = 4′-(4-hydroxyphenyl)-2,2′:6′,2′'-terpyridine) that behaves as a single-ion magnet (SIM) and displays two well-separated relaxation processes with the zero-field effective energy barriers of 372.5 and 529.8 K, which represents the record thermal relaxation barrier among the reported one-dimensional Dy^III-based systems containing only one spin center. A magnetic hysteresis loop up to 6.0 K at a sweep rate of 200 Oe s^-1 is also observed. To explore the origin of these distinct relaxations, two crystallographically isostructural analogues including diamagnetic Y^III- (2) and Y^III-doped Dy_0.2Y_0.8 (3) were prepared and characterized structurally and magnetically. The persistence of bimodal peaks in the out-of-phase magnetic susceptibility (χ″) of diluted sample 3 indicates that the dual-step relaxation behavior primarily originates from the single-ion anisotropy of Dy^III ions. Structural analyses combined with XRD pattern comparisons pre- and post-magnetic measurements elucidated that the dual-step relaxation in complex 1 is related to partially desolvated samples. This work sheds light on the multiple relaxation mechanism and further provides important information for the development of high-performance SMMs.