Fine-tuning emission color of aggregation-induced emission-active Ir(III) phosphors through simple ligand modification

Abstract The emission color is a crucial parameter to evaluate the performances of luminescent materials, thus seeking out the effective control method for illuminating color is an important issue. To further explore the relationship between emission colors and structure of aggregation-induced emission (AIE)-active phosphors, cationic Ir(III) complexes comprising the same ancillary ligand but different 1-phenyl-1H-pyrazole derivatives as cyclometalated ligands, were designed and synthesized. The experimental results show that all complexes exhibit outstanding AIE characters and their emission colors can be adjusted by simply changing their cyclometalated ligands. However, different from previous strategy, modifying main ligands only changes the energy level of lowest unoccupied molecular orbital rather than that of highest occupied molecular orbital. Combining this result and our reported approach, a strong blue-emitting AIE-active Ir(III) complex is successfully constructed. In addition, we observed that all complexes upon mechanical grinding exhibit remarkable and reversible mechanochromic luminescence behavior.