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

The photophysical tuning is reported for a series of tetraphenylphosphonium (TPP) metal halide hybrids containing distinct metal halides, TPP MX (MX =SbCl , MnCl , ZnCl , ZnCl Br , ZnBr ), 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 SbCl and MnCl , but significantly enhanced for the hybrids containing wide band gap non-emissive ZnCl . Structural and photophysical studies reveal that the enhanced afterglow is attributed to stronger π-π stacking and intermolecular electronic coupling between TPP cations in TPP ZnCl than in the pristine organic ionic compound TPPCl. Moreover, the afterglow in TPP ZnX 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.