Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center , Northwestern University , Evanston , Illinois 60208-3113 , United States.
Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center , Yale University , New Haven , Connecticut 06520 , United States.
J Am Chem Soc. 2018 Apr 18;140(15):5290-5299. doi: 10.1021/jacs.8b01778. Epub 2018 Apr 6.
We demonstrate that the 10-phenyl-10 H-phenothiazine radical cation (PTZ) has a manifold of excited doublet states accessible using visible and near-infrared light that can serve as super-photooxidants with excited-state potentials is excess of +2.1 V vs SCE to power energy demanding oxidation reactions. Photoexcitation of PTZ in CHCN with a 517 nm laser pulse populates a D electronically excited doublet state that decays first to the unrelaxed lowest electronic excited state, D' (τ < 0.3 ps), followed by relaxation to D (τ = 10.9 ± 0.4 ps), which finally decays to D (τ = 32.3 ± 0.8 ps). D' can also be populated directly using a lower energy 900 nm laser pulse, which results in a longer D'→D relaxation time (τ = 19 ± 2 ps). To probe the oxidative power of PTZ photoexcited doublet states, PTZ was covalently linked to each of three hole acceptors, perylene (Per), 9,10-diphenylanthracene (DPA), and 10-phenyl-9-anthracenecarbonitrile (ACN), which have oxidation potentials of 1.04, 1.27, and 1.6 V vs SCE, respectively. In all three cases, photoexcitation wavelength dependent ultrafast hole transfer occurs from D, D', or D of PTZ to Per, DPA, and ACN. The ability to take advantage of the additional oxidative power provided by the upper excited doublet states of PTZ will enable applications using this chromophore as a super-oxidant for energy-demanding reactions.
我们证明，10-苯基-10H-吩噻嗪自由基阳离子（PTZ）具有多种可用可见光和近红外光激发的激发双重态，这些激发态可作为超光氧化剂，具有超过+2.1 V vs SCE 的激发态势，可用于驱动需要能量的氧化反应。在 CHCN 中用 517nm 激光脉冲光激发 PTZ，首先将其激发到未弛豫的最低电子激发态 D'（τ < 0.3 ps），然后再弛豫到 D（τ = 10.9 ± 0.4 ps），最后再弛豫到 D（τ = 32.3 ± 0.8 ps）。也可以使用较低能量的 900nm 激光脉冲直接激发 D'，从而导致 D'→D 弛豫时间延长（τ = 19 ± 2 ps）。为了探测 PTZ 光激发双重态的氧化能力，将 PTZ 共价连接到三个空穴受体中的每一个上，这三个空穴受体分别是苝（Per）、9,10-二苯基蒽（DPA）和 10-苯基-9-蒽甲腈（ACN），它们的氧化电势分别为 1.04、1.27 和 1.6 V vs SCE。在所有三种情况下，光激发波长依赖性超快空穴转移均发生在 PTZ 的 D、D'或 D 与 Per、DPA 和 ACN 之间。利用 PTZ 上激发双重态提供的额外氧化能力的能力将使该生色团能够用于需要能量的反应的超氧化剂。
