AIE-active heteroleptic iridium complexes showing piezochromic luminescence

• Published in: Journal of molecular structure Vol. 1287; p. 135712
• Main Authors: Song, Zhongming, Xu, Xiangpin, Zhao, Nianyu, Cao, Chenhui, Zhang, Yuyang, Liu, Lei, Mao, Yueyuan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.09.2023
• Subjects: AIE; Iridium complexes; PCL; Iridium complexes; PCL; AIE
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2023.135712

•Two new iridium complexes with aggregation-induced emission (AIE) properties were designed and synthesized.•Piezochromic luminescence (PCL) properties of iridium complexes are regulated by different methyl-modified cyclometalated ligands. In this work, two heteroleptic iridium complexes Ir(L)2PyC4BCz named Ir-1 and Ir-2 were designed and synthesized, where L stands for 2-(4-methylphenyl)pyridine and 4-methyl-2-phenylpyridine, respectively; PyC4BCz for 9-(4-(4,5-dimethyl-2-(pyridin-2-yl)-1H-imidazolyl)butyl)-9H-carbazole. Their photophysical properties were investigated. The two complexes show good aggregation-induced emission (AIE) features. Nanoparticles in solution are related to their AIE properties. The mechanism of piezochromic luminescence (PCL) of complex Ir-2 was explored. On the one hand, strong intermolecular interactions are formed by hydrogen bonds in crystal. On the other hand, PXRD data indicate that the distance between molecules and disordered molecular arrangement can be changed by external mechanical grinding. According to DFT calculation and UV–vis diffuse reflectance spectra, we found that the PCL was ascribed to the intermolecular charge-transfer and the change of energy gap. [Display omitted]