Super-Ionic Conductive Magnet Based on a Cyano-Bridged Mn–Nb Bimetal Assembly

A two-dimensional manganese-octacyanoniobate
based magnet, MnII3[NbIV(CN)8]2(4-aminopyridine)10(4-aminopyridinium)2·12H2O, was prepared. This compound shows
a spin-flip transition
with a critical magnetic field value of ca. 200 Oe, which originates
from metamagnetism. In addition, an impedance measurement indicates
that this compound is a super-ionic conductor with 4.6 × 10–4 S cm–1. The observed super-ionic
conductivity is explained by the proton conduction (so-called the
Grotthuss mechanism) through the hydrogen-bonding network, i.e., Lewis
acidity of the Mn ion accelerates the deprotonation of the ligand
water molecules, and then the released proton propagates via ligand
water molecules, noncoordinated water molecules, and 4-aminopyridinium
cations.