Effect of Solvent Coordination on the Structural Transformation and Photoluminescence Properties of Hybrid Metal Halide: (TMS) ₂ SbBr ₅

Understanding the relationship among polyhedral distortion, bonding interactions in inorganic polyhedra, and emission properties in hybrid metal halides is essential for designing and developing new materials for optoelectronic applications. Herein, we report the effect of solvent coordination on the structural transformation from zero-dimensional (0D) (TMS)₂SbBr₅(DMSO) to one-dimensional (1D) (TMS)₂SbBr₅ [TMS⁺ = (CH₃)₃S⁺, DMSO = OS(CH₃)₂] and their photoluminescence properties. In (TMS)₂SbBr₅(DMSO), antimony (Sb) is coordinated with five bromine atoms and one solvent DMSO molecule via an oxygen atom to form isolated [SbBr₅(DMSO)]^2- polyhedra, resulting in a 0D structure. The 0D compound containing isolated [SbBr₅(DMSO)]^2- polyhedra transforms into corner-shared SbBr₆^3- octahedra, resulting in 1D [SbBr₅]_<i>n</i>^2<i>n</i>- zigzag chains along the <i>b</i>-axis upon controlled heating. Optical property studies and theoretical calculations show an indirect band gap for both compounds. Unlike most hybrid metal halides, superior emission properties are observed for the 1D (TMS)₂SbBr₅, with a photoluminescence quantum yield (PLQY) of ∼22%, compared to 0D (TMS)₂SbBr₅(DMSO) (PLQY = 4%), as determined from photoluminescence (PL) studies. Bonding of the solvent DMSO via higher electronegative oxygen with antimony in 0D (TMS)₂SbBr₅(DMSO) reduces the expression of the 5s² lone-pair effect of Sb³⁺, as evident from theoretical studies, which is attributed to its inferior luminescence properties compared to the 1D (TMS)₂SbBr₅.