Synthesis of isophthalic acid-carbazole coordination polymers with stacking-dependent ultralong room temperature phosphorescence and white-light emission

Exploiting the relationship between the stacking modes of molecules and room-temperature phosphorescence (RTP) performance is of great important to design afterglow materials. A series of coordination polymers [Cd(CzIP)] (1) (H2CzIP = 5-(carbazol-9-yl) isophthalate), [Cd(CzIP)(DMI)] (2) (DMI = 1,3-Dimethyl-2-imidazolidinone) and [Cd2(CzIP)2(H2O)2] (3) base on carbazole–isophthalic acid are synthesized via a solvothermal method. These compounds exhibit stacking-dependent RTP. Compounds 1 and 2 exhibit obvious time-dependent RTP with the afterglow color from orange to green, and show white-light emission owing to fluorescence and phosphorescence dual emission. Compound 3, which features the strong π‒π stacking, showed the weakest phosphorescence with the shortest lifetime. It reveals that the phosphorescence efficiency is not proportional to the overlap of π-π stacking, the triplet excited states of discrete dimer mode rather than H-aggregation can dominate the generation of room-temperature phosphorescence. These results indicate that coordination induction is an efficient approach to regulate the aggregation of chromophores, further modulating the room-temperature phosphorescence.