Tuning the Structure and Photoluminescence of [SbCl]-Based Halides via Modification of Imidazolium-Based Cations.

Structure-property relationships in imidazolium-based hybrid Sb(III) chlorides provide critical guidance for designing high-performance materials. Three zero-dimensional metal halides, namely, [Cmmim]SbCl (, [Cmmim] = 1-propyl-2,3-dimethylimidazolium), [Cmmim]SbCl (, [Cmmim] = 1-pentyl-2,3-dimethylimidazolium), and [Cmim]SbCl (, [Cmim] = 1-pentyl-3-methylimidazolium), are synthesized by ionothermal methods. These compounds exhibit markedly distinctly photophysical properties at their optimal excitation wavelengths. Structural analyses reveal that elongated alkyl chains in compounds and increase Sb-Sb distances compared to that in , effectively isolating [SbCl] units, suppressing inter-center energy transfer, and reducing non-radiative transitions, thereby enhancing the photoluminescence quantum yield (PLQY). Furthermore, methyl substitution at the C2-position of the imidazolium ring in compounds and induces asymmetric coordination environments around the [SbCl] emission centers, leading to pronounced structural distortion. This distortion promotes non-radiative decay pathways and diminishes luminescent efficiency. Furthermore, temperature-dependent spectroscopy analysis and fitting of the Huang-Rhys factor () reveal significant electron-phonon coupling in compounds -, which effectively promotes the formation of self-trapped excitons (STEs). However, compound exhibits extremely high , which significantly enhances phonon-mediated non-radiative decay and ultimately reduces its PLQY. Overall, compound has the highest PLQYs.