Bromine heavy-atom induced persistent room temperature phosphorescence of [ZnBr2] based coordination polymer

Abstract Molecule-based room temperature phosphorescence (RTP) materials have attracted considerable attention owing to their extensive applications in the optoelectronic and biological field. In this paper, two isostructural coordination polymers [Zn3(TIB)2X6] (X = Cl, 1-Cl; X = Br, 1-Br) have been synthesized and characterized by the assemble of triangular D-A-D ligand 1,3,5-tri(1H-imidazol-1-yl)benzene (TIB) and ZnX2 salts. The incorporation of halogen atoms play significant role in the formation of abundant C-H···X hydrogen-bonding interactions and dense structures, enable high thermal stability of the two complexes. 1-Br shows phosphorescence lifetime three order of magnitude longer than that of 1-Cl, and obviously phosphorescence emission recognized by naked eyes. The theory calculations reveal complete separation of molecular orbitals between halogen atoms and TIB ligand. Photoelectron response performance have also been studied. This work provides an efficient way to achieve long-last RTP by the incorporation of metal-bromide units in the coordination polymers.