Supercooled Liquid Phases of Luminescent Zero Dimensional Metal Halide Hybrids

Chemical design of metal halide hybrids (MHHs) with suppressed melting point (T_m) allows access to glassy phases from their liquid-melts. Thermal phase change (crystal-melt-glass) properties of glassy MHHs (with glass transition temperature T_g > room temperature) have been exploited for device applications. However, room temperature stable supercooled liquid (SCL) MHHs (with T_g < room temperature), originating from glass-SCL phase change, remain inaccessible. Here, a molecular design strategy is reported to access ambient stable, melt-processable, SCL multimetallic bromide hybrids (Mn²⁺,Cd²⁺; Mn²⁺,Zn²⁺; Benzyltributylammonium) with low T_g (15-16 °C), low T_m (90-100 °C), green luminescence, and high optical transparency. Structural, optical, thermal, and computational analyses highlight chemical design principles and support dopant (Mn²⁺) based luminescence. Rheological measurements confirm the SCL phase that shows thermal hysteresis and estimate relaxation time scales. This work provides a new material platform showcasing enhanced melt-processability for fabrication of moldable devices, unravelling chemical makeup-property correlation and expanding the material phase types of MHHs.