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oai:figshare.com:article/34050484 2026-10-01T21:03:52Z category_1 category_4 category_915 category_21 category_873 category_45 portal_63 item_type_3 month_year_10_2026

Effect of Aryl Substituents in Pyridyl-Imidazopyridine Ligands on the Aggregation-Induced Emission of Organoiridium(III) Complexes: Implications of 3MLCT and 3ILCT Excited States Monosh Rabha (5129705) Khanindram Baruah (10783573) Deikrisha Lyngdoh Lyngkhoi (25158766) Themmila Khamrang (5775641) Rakshantha Srithar (25158769) Susnata Pramanik (3345764) Snehadrinarayan Khatua (1446796) Biophysics Biochemistry Physical Sciences not elsewhere classified Biotechnology Chemical Sciences not elsewhere classified Sociology photophysical studies revealed optimized structure showed offers valuable guidelines nearly parallel arrangement ilct excited states characterized using spectroscopic cell imaging studies ray diffraction analysis biological response analysis strong emission enhancement show emission due exhibited weak emission displayed pronounced aggregation three cyclometalated iridium 3 </ sup cyclometalated iridium crystallographic analysis induced emission luminescent iridium unusual fluorescence successfully employed rich mixtures remained nonemissive rational design quenching mechanism naphthyl substituents lc state imidazopyridine ligands crystal x based materials aggregation state aggregated state In this study, three cyclometalated iridium(III) complexes, 1[PF6], 2[PF6], and 3[PF6], incorporating 3-aryl-substituted pyridyl imidazopyridine ligands, were synthesized and characterized using spectroscopic and single-crystal X-ray diffraction analysis. Photophysical studies revealed that the complexes 1[PF6] and 2[PF6] exhibited weak emission in acetonitrile but displayed pronounced aggregation-induced emission (AIE) in water-rich mixtures, whereas 3[PF6] remained nonemissive both in solution and in the aggregation state. Crystallographic analysis and DFT-optimized structure showed that the nearly parallel arrangement of the anthracenyl and 2-phenylpyridine moieties restricts intramolecular motion in 3[PF6] both in solution and aggregated state but does not show emission due to the population of a dark 3LC state. In contrast, the phenyl and naphthyl substituents in 1[PF6] and 2[PF6] undergo greater intramolecular motion in dilute solution, while their restriction upon aggregation promotes a strong emission enhancement. Additionally, biological response analysis of complexes 1[PF6] and 2[PF6] demonstrated low cytotoxicity toward HeLa cells and the complexes were successfully employed for live-cell imaging studies. This work provides new insights into an unusual fluorescence-quenching mechanism in cyclometalated iridium(III) complexes and offers valuable guidelines for the rational design of luminescent iridium-based materials. 2026-10-01T00:00:00Z Dataset Dataset 10.1021/acs.organomet.6c00217.s001 https://figshare.com/articles/dataset/Effect_of_Aryl_Substituents_in_Pyridyl-Imidazopyridine_Ligands_on_the_Aggregation-Induced_Emission_of_Organoiridium_III_Complexes_Implications_of_sup_3_sup_MLCT_and_sup_3_sup_ILCT_Excited_States/34050484 CC BY-NC 4.0