Chemical Excision of Tetrahedral FeSe₂ Chains from the Superconductor FeSe: Synthesis, Crystal Structure, and Magnetism of Fe₃Se₄(en)₂

Fragments of the superconducting FeSe layer, FeSe₂ tetrahedral chains, were stabilized in the crystal structure of a new mixed-valent compound Fe₃Se₄(en)₂ (en = ethylenediamine) synthesized from elemental Fe and Se. The FeSe₂ chains are separated from each other by means of Fe­(en)₂ linkers. Mössbauer spectroscopy and magnetometry reveal strong magnetic interactions within the FeSe₂ chains which result in antiferromagnetic ordering below 170 K. According to DFT calculations, anisotropic transport and magnetic properties are expected for Fe₃Se₄(en)₂. This compound offers a unique way to manipulate the properties of the Fe–Se infinite fragments by varying the topology and charge of the Fe-amino linkers