Ferromagnetic Polarization: The Quantum Picture of Switching On/Off Single-Molecule Magnetism

The mixed 3d–4f pentanuclear complex (Bu₄N)­[Mn^III₄Y^III(shi)₄(OAc)₄(CH₃OH)₄]·CH₃OH·H₂O (<b>1</b>) (H₃shi = salicylhydroxamic acid) was synthesized by the direct reaction of Y­(NO₃)₃·6H₂O, Mn­(OAc)₂·4H₂O, and H₃shi. When an additional ligand, (NHBu₃)₃[W­(CN)₈]·2H₂O, was added, the mixed 3d–4f–5d hexanuclear complex (Et₄N)₅[Mn^III₄Y^III(shi)₄(OAc)₄W^V(CN)₈]­(WO₄)_0.5 (<b>2</b>) was obtained. X-ray crystallographic analysis shows that the 3d–4f complex <b>1</b> represents a 12-metallacrown-4 (12-MC-4) structure, in which the metallacrown ring [Mn–N–O]₄ connection captures one Y^III ion with four bridging acetate anions, completing the eight-coordinated environment around Y^III ion, while four methanol molecules each coordinate to the Mn^III ions on the other side of the Y^III ion. After octacyanotungstate is introduced, the [W^V(CN)₈] group substitutes for four methanol molecules of <b>1</b> to form complex <b>2</b>. Magnetic studies indicate the overall antiferromagnetic coupling present within the MC ring of complex <b>1</b>. However, interestingly, the dominant ferromagnetic coupling between Mn^III ions was observed in complex <b>2</b>. A susceptibility analysis shows that the natural spin alignments in 12-MC-4 metallacrowns are tuned from overall antiferromagnetic to dominant ferromagnetic fashions by magnetic coupling between Mn^III ions and the W^V ion. Complex <b>1</b> [Mn^III₄Y^III] retains an <i>S</i> = 0 ground state, and complex <b>2</b> [Mn^III₄Y^IIIW^V] shows obvious single-molecule magnet (SMM) behavior with an <i>S</i>_T = 11/2 ground state, respectively, before and after introduction of the octacyanotungstate group. The spin frustration geometrical structure constructed by four Mn^III ions and one W^V ion was considered as the key factor for switching on the SMM properties of the 12-MC-4 system

Electrochemical Synthesis and Magnetic Properties of [Cu₉W₆]: The Ultimate Member of the Quindecanuclear Octacyanometallate-Based Transition-Metal Cluster?

[Cu₉W₆], synthesized by the electrochemical method, may be the ultimate member of the quindecanuclear octacyanometallate-based transition-metal cluster. Its single-crystal structure and magnetic properties were characterized