Metal halide regulated photophysical turning of zero-dimensional organic metal halide hybrids: from efficient phosphorescence to ultralong afterglow.

Zero-dimensional (0D) organic metal halide hybrids have emerged as a new class of luminescent materials with exceptional structural and photophysical tunability, thanks to the rich choices of organic cations and metal halides for the formation of ionically bonded systems. Here we report photophysical tuning of a series of tetraphenylphosphonium (TPP) metal halide hybrids containing distinct metal halides, TPP 2 MX n (MX n = SbCl 5 , MnCl 4 , ZnCl 4 , ZnCl 2 Br 2 , ZnBr 4 ), from efficient phosphorescence to ultralong afterglow. It is found that the afterglow properties of TPP + cations could be suspended for the hybrids containing low bandgap emissive metal halide species, such as SbCl 5 2- and MnCl 4 2- , but significantly enhanced for the hybrids containing wide bandgap non-emissive ZnCl 4 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 TPP 2 ZnCl 4 than in the pristine organic ionic compound TPPCl. Moreover, the afterglow in TPP 2 ZnX 4 can be tuned by controlling the halide composition, with the change from Cl to Br resulting in a shorter afterglow due to heavy atom effect.