A Cyanide-Bridged\nFeCo<sub>5</sub> Square-Pyramidal\nSingle-Ion Magnet

The reaction of mononuclear [Co<sup>II</sup>(Me<sub>6</sub>tren)Cl]<sup>+</sup> precursors and diamagnetic [Fe<sup>II</sup>(CN)<sub>6</sub>]<sup>4–</sup> building blocks affords a cyanide-bridged\nhexanuclear <b>FeCo</b><sub><b>5</b></sub> complex featuring\nsquare-pyramidal\narchitecture. The dc magnetic susceptibility data and theoretical\ncalculations reveal that the complex exhibits a well-isolated <i>S</i> = 15/2 ground state composed of c-coupled <i>S</i> = 3/2 Co<sup>2+</sup> ions. The ac magnetic susceptibility data\nfurther reveal that the complex exhibits slow magnetic relaxation\nunder an applied field due to the presence of considerable easy-axis\nmagnetic anisotropy of the five Co<sup>2+</sup> ions. As far as is\nknown, complex <b>FeCo</b><sub><b>5</b></sub> is the first\nsquare-pyramidal hexanuclear single-ion magnet.