Metal Halide Regulated Photophysical Tuning of Zero‐Dimensional Organic Metal Halide Hybrids: From Efficient Phosphorescence to Ultralong Afterglow

Abstract

The photophysical tuning is reported for a series of tetraphenylphosphonium (TPP) metal halide hybrids containing distinct metal halides, TPP₂ MX_n (MX_n =SbCl₅ , MnCl₄ , ZnCl₄ , ZnCl₂ Br₂ , ZnBr₄ ), from efficient phosphorescence to ultralong afterglow. The afterglow properties of TPP⁺ cations could be suspended for the hybrids containing low band gap emissive metal halide species, such as SbCl₅ ^2- and MnCl₄ ^2- , but significantly enhanced for the hybrids containing wide band gap non-emissive ZnCl₄ ^2- . Structural and photophysical studies reveal that the enhanced afterglow is attributed to stronger π-π stacking and intermolecular electronic coupling between TPP⁺ cations in TPP₂ ZnCl₄ than in the pristine organic ionic compound TPPCl. Moreover, the afterglow in TPP₂ ZnX₄ can be tuned by controlling the halide composition, with the change from Cl to Br resulting in a shorter afterglow due to the heavy atom effect.