Polar crystal structures have attracted
more and more attention, due to their unique characteristics, such
as ferroelectricity, piezoelectricity, and nonlinear optical property,
etc. However, the construction of polar materials is always accidental,
and finding an effective synthesis strategy to construct polar materials
remains a challenge. Herein, inorganic–organic hybrid compounds
of [C7H14N][FeCl4] (1) ([C7H14N] = quinuclidinium cation) and [C7H14N][GeCl3] (2) were prepared,
respectively, to verify the beneficial effect of polar anions on the
construction of polar crystals. Compound 1 crystallized
in the Pbca space group, while 2 belongs
to the P43 space group at room temperature.
Investigation into the structure of 2 reveals that the
polarity of 2 derives from the triangular pyramid structure
of [GeX3]− with lone pair electrons.
Meanwhile, 2 undergoes a phase transition from the P43 space group to the center Pm
m at 385 K, leading to the
optic–electric switching property. Thus, the present work exhibits
the advantage of [GeX3]− as the inorganic
constituent component in the hybrid polar materials and provides an
effective approach for the construction of a polar molecule-based
crystal with a switchable property.