A Photochromic Organic–Inorganic Hybrid Schiff Base Metal Halide Ferroelectric

Integration of photochromism and
ferroelectricity in one material
is significant for not only an in-depth understanding of the physiochemical
process but also advances in multipurpose optoelectronic devices.
Research on the combination of them has been mainly constrained in
ferroelectric liquid crystals doped with photochromic components,
ferroelectric ceramics doped with rare-earth ions, and single-component
organic photochromic crystals, leading to scant material diversity
and limited application range. Recently booming organic–inorganic
hybrid materials may serve as potential candidates for neoteric photochromic
ferroelectrics due to their species diversity, easy chemical fabrication,
and versatile physical properties. In this work, two new organic–inorganic
hybrid metal halide Schiff base derivatives of [SAPD]2CdX4 (SAPD = 1-((2-hydroxybenzylidene)­amino)­pyridin-1-ium, X =
Br and I) have been successfully synthesized. Both of them present
reversible photochromism, originating from the photoinduced proton
transfer and structural isomerization. More interestingly, [SAPD]2CdI4 exhibits room-temperature ferroelectricity,
which has extended the photochromic ferroelectric family. Besides,
optically controlled polarization switching has been achieved in [SAPD]2CdI4, demonstrating the ability of modulation of
ferroelectricity via a photoinduced structural change. This work provides
inspiration for the combination of functionalities in hybrid materials,
which holds great potential for intriguing optoelectronic integrated
applications.