Photochemistry of 2-Formylphenylnitrene: A Doorway to Heavy-Atom Tunneling of a Benzazirine to a Cyclic Ketenimine
Photochemistry of 2-Formylphenylnitrene: A Doorway to Heavy-Atom Tunneling of a Benzazirine to a Cyclic Ketenimine
复制标题
DOI：
10.1021/jacs.7b10495
复制
发表时间：
2017-12-06
影响因子：
15
通讯作者：
Fausto, Rui
中科院分区：
文献类型：
--
作者：
Nunes, Claudio M.;Reva, Igor;Fausto, Rui
芳基硝基化合物光滑的势能面揭示了意想不到的有趣的反应。要探索这样一个具有挑战性的表面，一种有效的方法是使用低温基质环境和可调窄带辐射源的组合。通过这种方法，我们发现了重原子隧穿反应，该反应涉及稠环苯并氮杂环为七元环环酮亚胺的自发扩环反应。在Ar基质中分离出的氚和氚三重态2-甲酰基苯基氮通过光化学原位生成苯并嗪。扩环反应在10K下进行，反应速率常数为7.4×10~(-7)S(~(-1))，而活化势垒为7.5千卡·摩尔~(-1)。计算的速率常数证实，在低温条件下，反应只能通过基态的隧穿过程才能发生。研究还发现，当样品受到宽带红外辐射时，扩环反应速度快1个数量级以上。
The slippery potential energy surface of aryl nitrenes has revealed unexpected and fascinating reactions. To explore such a challenging surface, one powerful approach is to use a combination of a cryogenic matrix environment and a tunable narrowband radiation source. In this way, we discovered the heavy-atom tunneling reaction involving spontaneous ring expansion of a fused-ring benzazirine into a seven-membered ring cyclic ketenimine. The benzazirine was generated in situ by the photochemistry of protium and deuterated triplet 2-formylphenylnitrene isolated in an argon matrix. The ring expansion reaction takes place at 10 K with a rate constant of,similar to 7.4 x 10(-7) s(-1), despite an estimated activation barrier of 7.5 kcal mol(-1\). Moreover, it shows only a marginal increase in the rate upon increase of the absolute temperature by a factor of 2. Computed rate constants with and without tunneling confirm that the reaction can only occur by a tunneling process from the ground state at cryogenic conditions. It was also found that the ring expansion reaction rate is more than 1 order of magnitude faster when the sample is exposed to broadband IR radiation.