Polyoxometalates (POMs) with various coordination fashions are versatile ligands for constructing single-ion magnets (SIMs), but enforcing POM-SIMs with a specific geometry remains a synthetic challenge. Herein, we synthesized a POM-cocrystallized Dy-SIM [Dy(OPPh)(HO)][PWO]·4EtOH () and a POM-ligated Dy-SIM [{Dy(OPPh)(HO)}{PWO}]·PhPO·HO () with pentagonal bipyramidal local coordination geometry. Magnetic measurements indicate that displays field-induced single-molecule magnet (SMM) behavior and the relaxation is dominated by under-barrier processes. exhibits spin-lattice relaxation at a broader temperature region with a reversal barrier over 300 K. Magneto-structural analysis reveals that the enhancement of SMM behavior originated from the equatorial replacement of PhPO by POM, which strengthens the axial anisotropy in . Luminescent experiments indicate that the characteristic Dy emissions of are covered up by the strong π-π* emission of PhPO at low-temperature regions. As for , partial Dy emission persists thanks to the antenna effect between Dy and POM.
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