铱
化学
二苯甲酮
芳基
激发态
光敏剂
溴化物
取代基
电子转移
光化学
催化作用
有机化学
烷基
物理
核物理学
作者
Jong-Hwa Shon,Steven Sittel,Thomas S. Teets
标识
DOI:10.1021/acscatal.9b02759
摘要
A series of potent bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands is described. Structure–property analysis reveals that substituent modification of the NacNac ligands has a large effect on the ground-state IrIV/IrIII potential, which shifts cathodically as the NacNac is made more electron-rich. In addition, the excited-state IrIV/*IrIII potentials are ca. 300–500 mV more negative than that of fac-Ir(ppy)3 (ppy = 2-phenylpyridine), indicating that these compounds have much more reducing excited states. Rate constants for excited-state electron transfer between these photosensitizers and benzophenone are ∼2–3 times faster than fac-Ir(ppy)3, demonstrating that these complexes are both kinetically and thermodynamically more potent for excited-state electron transfer. We use these photosensitizers to optimize a simple reaction procedure for photocatalytic debromination of aryl bromide substrates, which requires only the photosensitizer, blue light, and an amine base, without silanes or other additives that are used in previously reported methods.
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