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Phosphorescent Cationic Iridium(III) Complexes with 1,3,4-oxadiazole Cyclometalating Ligands: Solvent-Dependent Excited-State Dynamics
夏安东
Author NameAffiliationE-mail
夏安东 中国科学院化学所 andong@iccas.ac.cn 
Abstract:
Aiming at elucidating the nature of low-lying triplet states and the effect of ligand modifications on the excited-state properties of functional cationic iridium complexes, the solvent-dependent excited-state dynamics of two phosphorescent cationic iridium(III) complexes, namely [Ir(dph-oxd)2(bpy)]PF6 (1) and [Ir(dph-oxd)2(pzpy)]PF6 (2), were investigated by femtosecond and nanosecond transient absorption spectroscopy. Upon photoexcitation to the metal-to-ligand charge-transfer (MLCT) states, the excited-state dynamics show a rapid process (τ = 0.7–3 ps) for the formation of solvent stabilized 3MLCT states, which significantly depends on the solvent polarity for both 1 and 2. Sequentially, a relatively slow process assigned to the vibrational cooling/geometrical relaxation and a long-lived phosphorescent emissive state are identified. Due to the different excited-state electronic structures regulated by ancillary ligands, the solvation-induced stabilization of the 3MLCT state in 1 is faster than that in 2. The present results provide a better sight of excited-state relaxation dynamics of ligand-related iridium(III) complexes and solvation effects on triplet manifolds.
Key words:  iridium complex, phosphorescence, metal-to-ligand charge transfer, transient absorption, solvation
FundProject:
Phosphorescent Cationic Iridium(III) Complexes with 1,3,4-oxadiazole Cyclometalating Ligands: Solvent-Dependent Excited-State Dynamics
夏安东
摘要:
Aiming at elucidating the nature of low-lying triplet states and the effect of ligand modifications on the excited-state properties of functional cationic iridium complexes, the solvent-dependent excited-state dynamics of two phosphorescent cationic iridium(III) complexes, namely [Ir(dph-oxd)2(bpy)]PF6 (1) and [Ir(dph-oxd)2(pzpy)]PF6 (2), were investigated by femtosecond and nanosecond transient absorption spectroscopy. Upon photoexcitation to the metal-to-ligand charge-transfer (MLCT) states, the excited-state dynamics show a rapid process (τ = 0.7–3 ps) for the formation of solvent stabilized 3MLCT states, which significantly depends on the solvent polarity for both 1 and 2. Sequentially, a relatively slow process assigned to the vibrational cooling/geometrical relaxation and a long-lived phosphorescent emissive state are identified. Due to the different excited-state electronic structures regulated by ancillary ligands, the solvation-induced stabilization of the 3MLCT state in 1 is faster than that in 2. The present results provide a better sight of excited-state relaxation dynamics of ligand-related iridium(III) complexes and solvation effects on triplet manifolds.
关键词:  iridium complex, phosphorescence, metal-to-ligand charge transfer, transient absorption, solvation
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