Organosilicon cluster goes ferroelectric

Ferroelectrics and clusters have independently attracted significant attention as two important classes of functional materials. Bridging these two fields by introducing ferroelectricity into clusters offers a compelling strategy to overcome the intrinsic limitations of conventional small-molecule materials. However, cluster-based ferroelectrics remain exceedingly rare and challenging to realize. In this study, we report the construction of an organosilicon molecular cluster ferroelectric, aminopropyl isobutyl Si8O12 cluster (1), achieved by introducing distorted tetrahedral units with a polar –NH2 group. Crystal 1 undergoes a 3F1-type ferroelectric-ferroelastic phase transition at 328 K, accompanied by a distinct on/off switching behavior of optical birefringence. Comprehensive structural and physical characterizations confirm the coexistence of ferroelectricity and ferroelasticity. Remarkably, this multiferroic crystal demonstrates excellent thermal stability, high chemical robustness, a large number of polar axes, pronounced entropy change, and a low elastic modulus compared with previously reported organosilicon ferroelectric crystals. To the best of our knowledge, Crystal 1 is the first organosilicon cluster ferroelectric, establishing a new design paradigm for organosilicon and molecular ferroelectrics.