Guest-Activated Forbidden Tilts in a Molecular Perovskite Analogue

The manipulation of distortions in
perovskite structures is critical
to tailoring the properties of these materials for a variety of applications.
Here we demonstrate a violation of established octahedral tilt rules
in the double perovskite analogue (NH4)2SrFe­(CN)6·2H2O. The forbidden tilt pattern we observe
arises through coupling to hydration-driven Jahn–Teller-like
distortions of the Sr coordination environment. Access to novel distortion
mechanisms and the ability to switch these distortions on and off
through chemical modification fundamentally expands the toolbox of
techniques available for engineering symmetry-breaking processes in
solid materials.