Halogen Substitution Dual Regulation of Structure and Symmetry in an Edge-Shared ABX3 Hybrid Ferroelectric

Organic–inorganic hybrid ABX3-type ferroelectric materials with their structural versatility hold broad application prospects in optoelectronics, data storage, sensing, and other advanced fields. Despite chemical strategies targeting organic motifs that have proven effective for the rational design of novel hybrid molecular ferroelectrics, studies on halogen substitution receiving dual regulation of structure and symmetry in an edge-shared ABX3 hybrid ferroelectrics remain scarce. Herein, we synthesized a new one-dimensional ABX3 hybrid ferroelectric DMEIM-CdCl3 (DMEIM = N-(iodomethyl)-N,N-dimethylethylamine) by employing a halogen substitution strategy. This approach precisely tuned the crystal space group of the parent compound (centrosymmetric Pbca) to the ferroelectric Cc space group. Structurally, DMEIM-CdCl3 features one-dimensional [CdCl5]−n pyramidal chains composed of edge-shared CdCl5 hexahedra, deviating from the conventional ABX3 framework built from face- or corner-sharing polyhedra. DMEIM-CdCl3 undergoes a characteristic ferroelectric phase transition above room temperature (Tc = 379 K) with an Aizu notation of 2/mFm. This work offers insights into expanding the family of hybrid ferroelectric materials through rational chemical design.