Manipulating bistability in molecule level, especially via single-molecule magnets (SMMs) and spin-crossover (SCO) materials, has attracted enormous recent interests due to their multifaceted magnetic behaviours and potential applications in devices....
A stable and high-performance molecule displays a reversal barrier >900 K, which is the highest among square antiprismatic dysprosium single-ion magnets.
Stimuli‐responsive materials that can be reversibly switched by light are of immense interest. Among them, photo‐responsive spin crossover (SCO) complexes have great promises to combine the photoactive inputs with multifaceted outputs into switchable materials and devices. However, the reversible control the spin‐state change by photochromic guests is still challenging. Herein, we report an unprecedented guest‐driven light‐induced spin change (GD‐LISC) in a Hofmann‐type metal–organic framework (MOF), [Fe(bpn){Ag(CN)2}2]⋅azobenzene. (1, bpn=1,4‐bis(4‐pyridyl)naphthalene). The reversible trans–cis photoisomerization of azobenzene guest upon UV/Vis irradiation in the solid‐state results in the remarkable magnetic changes in a wide temperature range of 10–180 K. This finding not only establishes a new switching mechanism for SCO complexes, but also paves the way toward the development of new generation of photo‐responsive magnetic materials.
Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating, especially for singlemolecule magnets (SMMs). Herein a family of dysprosium single-ion magnets (SIMs) sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions, through which the subtle coordination geometry of Dy(III) can be finely tuned based on the size effect. The effective energy barrier (Ueff) successfully increases from 439 K to 632 K and the magnetic hysteresis temperature (under a 200 Oe/s sweep rate) raises from 11 K to 24 K. Based on the crystal-field theory, a semi-quantitative magneto-structural correlation deducing experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value 2 0 corresponding to the axial coordination bond lengths and the bond angles. Through the evaluation of the remanent magnetization from hysteresis, quantum tunneling of magnetization (QTM) is found to exhibit negative correlation with the structural-related value Stun corresponding to the axial coordination bond angles.
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