Polar ferromagnetic metal by intercalation of metal-amine complexes

The metal-amine complex Co(en)3, where en = ethylenediamine, intercalates between layers of cobalt sulfide (CoS) to form a polar, ferromagnetic metal. We solve the structure of the hybrid compound [Co(en)3](CoS)12·en in the polar group Pca21 with lattice parameters a = 14.778(3) Å, b = 11.066(3) Å, and c = 20.095(5) Å using single-crystal X-ray diffraction. The [Co(en)3]2+ complexes order between CoS layers and break their inherent fourfold symmetry. Moreover, the chiral Co(en)3 complexes hydrogen bond to the terminal sulfides of the layers and break inversion symmetry, thereby inducing a polar state. The shortest hydrogen bond of the amino group is H···S = 2.41(1) Å. From 1.8 to 300 K, the title compound displays metallic electrical resistivity and an anomaly at 43 K. Through magnetization measurements, we find that Co(en)3 exhibits spontaneous ferromagnetic order below 43 K. First-principles calculations reproduce the ferromagnetic structure and illustrate decoupling between the conducting electrons and the inversion-lifting distortion. Our work shows that hybrid materials created from intercalation chemistry of functional 2D hosts provides a pathway for uniting contraindicated properties.