Coordination-Induced Approach of a Carbazole-Based Molecule to Modulate Packing Modes for Ultralong Room-Temperature Phosphorescence

Controlling molecular packing is important to modulate the aggregate states and the optoelectronic characteristics. Here, we employ a coordination-driven self-assembly, two coordination polymers, [Cd2(CzIP)2(DMPU)2] (1) and [Cd2(CzIP)2(μ3-O)(H2O)2] (2) (CzIP = 5-(9H-carbazol-9-yl)-isophthalic acid, DMPU = N,N-dimethylpropyleneurea), were successfully synthesized. These two compounds exhibit a molecular packing-dependent emission. Compound 1, where CzIP molecules feature the monomer packing mode, exhibits dual emission, including blue fluorescence and ultralong phosphorescence at room temperature (RTP). The phosphorescence lifetime of compound 1 is 0.63 s at 553 nm under ambient conditions. However, compound 2 shows excimer-dominated green fluorescence emission without RTP. Importantly, it is demonstrated that the coordination-induced pattern opens a way for the development of organic optoelectronic properties by regulating the molecular packing modes.