Coexisting Ferroelectric and Ferroelastic Orders in Rare 3D Homochiral Hybrid Bimetal Halides

Molecular
multiferroics that simultaneously possess ferroelectric
and ferroelastic orders have sparked growing interest due to their
promising uses in shape memory devices, actuators, and sensors. However,
it is still a great challenge to effectively explore new molecular
multiferroic materials with multiple functionalities. Herein, by introducing
homochiral molecules as polar groups, we synthesized a new three-dimensional
(3D) bimetal halide multiferroic (R3HP)2RbBiBr6 (1; R3HP = R-3-hydroxypyrrolidinium).
Crystal 1 adopts a mixed face- and corner-sharing RbI/BiIII-centered 4-connected lon topology with a
Schläfli symbol of 66. A distinct symmetry breaking
with the 2F1 species leads to the emergence of ferroelasticity
and biaxial ferroelectricity. Such a 3D homochiral bimetal halide
combined with ferroelectricity and ferroelasticity is unprecedented.
Moreover, 1 exhibits fascinating circularly polarized
luminescence and semiconducting properties. This finding signifies
an important step toward exploring new hybrid molecular multiferroic
materials with the coexistence of ferroelectricity and ferroelasticity
and inspires their future multifunctional applications.