Achieving Combined Photoluminescence and SHG in a New Polar Hybrid Glass-Ceramic with Square-Pyramidal [SbBr₅] Units

Hybrid glass-ceramics have garnered extensive research interest due to their exceptional optical properties. Integrating luminescence and second harmonic generation (SHG) in hybrid glass-ceramics is of particular interest for designing advanced devices, but is challenging owing to the lack of design principles. In this study, we present two textbook-style comparative examples of hybrid antimony(III) bromides, (PPTPP)₂[Sb₂Br₈] (1) and (PPTPP)₂[SbBr₅] (2), where PPTPP⁺ = (3-phenylpropyl)(triphenyl)phosphonium. Compound 1 with centrosymmetric seesaw [Sb₂Br₈] dimers crystallizes in C2/c space group and is photoluminescently silent, whereas 2 with square-pyramidal [SbBr₅] monomers crystallizes in polar P2₁ space group and exhibits photoluminescence under excitation at 416 nm. Both 1 and 2 have higher thermostability with decomposition temperatures of 552 K, and undergo crystal-liquid-glass transitions upon heating and natural cooling, with melting temperatures of 445 and 484 K and vitrification temperatures of 331 and 340 K, respectively. Notably, the glassy sample of 2 exhibits an onset recrystallization temperature of 383 K, enabling the facile fabrication of a polar glass-ceramic (2-GC) thin film under ambient conditions. Crucially, 2-GC present the first example of a hybrid glass-ceramic system integrating luminescence (centered at 691 nm) and SHG (12.8 times stronger than that of its polycrystalline counterpart), pioneering an innovative route for designing multichannel materials.