University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal.
Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
J Am Chem Soc. 2021 Jun 9;143(22):8266-8271. doi: 10.1021/jacs.1c04329. Epub 2021 May 28.
H-tunneling is a ubiquitous phenomenon, relevant to fields from biochemistry to materials science, but harnessing it for mastering the manipulation of chemical structures still remains nearly illusory. Here, we demonstrate how to switch on H-tunneling by conformational control using external radiation. This is outlined with a triplet 2-hydroxyphenylnitrene generated in an N matrix at 10 K by UV-irradiation of an azide precursor. The -orientation of the nitrene's OH moiety was converted to by selective vibrational excitation at the 2ν(OH) frequency, thereby moving the H atom closer to the vicinal nitrene center. This triggers spontaneous H-tunneling to a singlet 6-imino-2,4-cyclohexadienone. Computations reveal that such fast H-tunneling occurs through crossing the triplet-to-singlet potential energy surfaces. Our experimental realization provides an exciting novel strategy to attain control over tunneling, opening new avenues for directing chemical transformations.
H 隧穿是一种普遍存在的现象，与生物化学到材料科学等领域都有关联，但如何利用它来掌握化学结构的操控仍然几乎是虚幻的。在这里，我们展示了如何通过外部辐射的构象控制来开启 H 隧穿。这是通过在 N 基质中用紫外线照射叠氮化物前体制备的三重态 2-羟基苯基氮烯来实现的。氮烯的 OH 部分的 -取向通过在 2ν(OH) 频率处的选择性振动激发转换为 ，从而使 H 原子更接近相邻的氮烯中心。这会触发 H 原子自发隧穿到单重态 6-亚氨基-2,4-环己二烯酮。计算表明，这种快速 H 隧穿是通过穿越三重态到单重态的势能面发生的。我们的实验实现提供了一种令人兴奋的新策略，可以实现对隧穿的控制，为指导化学转化开辟了新途径。
