Metal-Halide Coordination Polymers with Excitation Wavelength-and Time-Dependent Ultralong Room-Temperature Phosphorescence

Metal-organic hybrids with ultralong room-temperature phosphorescence (RTP) have potential applications in many fields, including optical communications, anticounterfeiting, encryption, bioimaging, and so on. Herein, we report two isostructural one-dimensional zinc-organic halides as coordination polymers ZnX2(bpp) (X = Cl, 1; Br, 2; bpp = 1,3-di(4-pyridyl)propane) with excitation wavelength- and time-dependent ultralong RTP properties. The dynamic multicolor afterglow can be assigned to the emission of the pristine ligand bpp and its interactions with halogen atoms. Experiments and theoretical calculations both suggest that ZnX2 is crucial for ultralong RTP: (a) the metal coordination and X center dot center dot center dot pi bonds in coordination polymers fix the bpp molecules and suppress the nonradiative transitions; (b) the spin-orbital coupling of coordination polymers is largely enhanced relative to the bpp because of the heavy atom effect; and (c) the charge transfer exists between halogens and bpp ligand. Therefore, this work not only presents metal-halide coordination polymers with excitation wavelength- and time-dependent RTP properties, but also provides a facile method for the new types of dynamic multicolor afterglow materials.

Automated summary

We report metal-organic hybrids with ultralong room-temperature phosphorescence (RTP), which have potential applications in various fields. The coordination polymers of zinc-organic halides exhibit excitation wavelength- and time-dependent ultralong RTP properties. Experimental and theoretical results suggest that metal coordination and spin-orbital coupling are crucial for achieving ultralong RTP in these materials. Moreover, a charge transfer exists between halogens and the organic ligand, contributing to the dynamic multicolor afterglow. This work not only presents a new type of material with unique properties, but also provides a facile method for the synthesis of dynamic multicolor afterglow materials.