Emerged Metallicity in Molecular Ferromagnetic Wires

Supramolecular
engineering bridges molecular assembly with macromolecular
charge-transfer salts, promising the design to construct supramolecular
architectures that integrate cooperative properties difficult or impossible
to find in conventional lattices. Here, we report the crystal engineering
design and kinetic growth of one-dimensional supramolecular wires
composed of bis­(ethylenedithio)­tetrathiafulvalene (ET+)
cation and polymeric Cu­[N­(CN)2]2– anion. A bulk ferromagnetic order is discovered for filling up the
gap where strong ferromagnetism is missing in such ET molecule-based
charge-transfer salts. Metallicity is induced by electric current
from the semiconducting wire, which is attributed to strain effect
by tuning its close molecular contact. This structural feature is
evidenced through the combination of various mechanistic spectroscopic
studies. Electric dipole is established from the close molecular contacts
and is suggestive to stabilize ferromagnetic spin interaction through
anions bridging spin sites. The breakthrough shown here provides a
pathway to explore low-dimensional supramolecular materials exhibiting
strong electron correlation, metallicity, and ferromagnetism.