Long-Range Ferroelectric Order Regulated by Cl–Cl Halogen Bonding in a 1D Ru-Based Hybrid Double Perovskite

Long-range order of electric dipoles means important physical properties such as ferroelectricity or antiferroelectricity, making materials have broad applications in information storage, sensors, switches, and optical electric devices. However, the orientation control of electric dipoles remains a great challenge on a molecular/ion level. Herein, we report the realization of ferroelectric order via Cl–Cl halogen-bond interactions in hybrid double perovskite [CH2ClN(CH3)3]2NaRuCl6 (TCNRC) derived from [(CH3)4N]2NaRuCl6 (TNRC) for the first time. TCNRC shows spontaneous polarization (Ps = 2.67 μC cm–2) and piezoelectricity (d33 = 4 pC N1–) with a Curie temperature (Tc) of 320 K. This study reveals the important role of halogen-bonding interactions to form ferroelectric orders and provides new insights into the molecular level regulatory polarity in molecular ferroelectric systems.