化学
磷光
激发态
铱
配体(生物化学)
光化学
噻吩
三氟甲基
立体化学
结晶学
荧光
有机化学
催化作用
烷基
受体
核物理学
物理
量子力学
生物化学
作者
Shin‐ya Takizawa,Sora Katoh,Atsushi Okazawa,Naoya Ikuta,Satoko Matsushima,Fanyang Zeng,Shigeru Murata
出处
期刊:Inorganic Chemistry
[American Chemical Society]
日期:2021-03-14
卷期号:60 (7): 4891-4903
被引量:7
标识
DOI:10.1021/acs.inorgchem.0c03802
摘要
A series of novel monocyclometalated [Ir(tpy)(btp)Cl]+ complexes (Ir2–Ir5) were synthesized using 2,2′:6′,2″-terpyridine (tpy) and 2-(2-pyridyl)benzo[b]thiophene (btp) ligands, as well as their derivatives bearing electron-donating tert-butyl (t-Bu) and electron-withdrawing trifluoromethyl (CF3) groups. Ir2–Ir5 exhibited visible-light absorption stronger than that of the known complex [Ir(tpy)(ppy)Cl]+ (Ir1; ppy = 2-phenylpyridine). Spectroscopic and computational studies revealed that two triplet states were involved in the excited-state dynamics. One is a weakly emissive and short-lived ligand to ligand charge-transfer (LLCT) state originating from the charge transfer from the btp to the tpy ligand. The other is a highly emissive and long-lived ligand-centered (LC) state localized on the btp ligand. Interestingly, the excited state dominant with 3LLCT was completely changed to the 3LC state upon the introduction of substituents on both the tpy and btp ligands. For instance, the excited state of the parent complex Ir2 was weakly emissive (Φ = 2%) and short-lived (τ = 110 ns) in CH2Cl2; conversely, Ir5, fully furnished with t-Bu and CF3 groups, displayed intense phosphorescence with a prolonged lifetime (τ = 14 μs). This difference became increasingly prominent when the solvent was changed to aqueous CH3CN, most probably due to the 3LLCT stabilization. The predominant excited-state nature was switchable between the 3LLCT and 3LC states depending on the substituents employed; this was demonstrated through investigations of Ir3 and Ir4, bearing either the t-Bu or the CF3 group, where the complexes exhibited properties intermediate between those of Ir2 and Ir5. All of the Ir(III) complexes were tested as photosensitizers in photocatalytic H2 evolution over a Co molecular catalyst, and Ir5 outperformed the others, including Ir1, due to improvement in the following key properties: visible-light-absorption ability, excited-state lifetime, and reductive power of the one-electron-reduced species against the catalyst.
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