Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
J Phys Chem A. 2015 Jan 8;119(1):67-78. doi: 10.1021/jp511208p. Epub 2014 Dec 22.
In the present work, the combined electronic structure calculations and dynamics simulations have been performed to explore the decomposition reactions of 2H-azirine, 2-phenyl-2H-azirine, and 3-phenyl-2H-azirine in gas phase. Thermal cleavage of the C-C single bond yields nitrile ylides as products with a high barrier (>50.0 kcal mol(-1)). On the other hand, photochemical cleavage reactions starting from the (1)nπ* state of 2H-azirine and 3-phenyl-2H-azirine are ultrafast nonadiabatic processes (<100 fs), leading to nitrile ylides through the S1/S0 conical intersection. The fast formation of ylides in experiments was well reproduced by present dynamics simulations. For 3-phenyl-2H-azirine, population of the S1((1)ππ*) state is another decay pathway for the S2((1)nπ*) state. The C-N bond cleavage upon photoexcitation was usually considered to take place in T1 state. However, our calculations reveal that photocleavage of the C-N single bond for 2-phenyl-2H-azirine is very likely to take place in S1 state. The present work provides new insights into photocleavage mechanism of 2H-azirine and the related derivatives.
在本工作中，我们进行了组合电子结构计算和动力学模拟，以探索 2H-氮丙啶、2-苯基-2H-氮丙啶和 3-苯基-2H-氮丙啶在气相中的分解反应。C-C 单键的热裂解生成腈叶立德作为产物，具有较高的势垒（>50.0 kcal mol(-1))。另一方面，从 2H-氮丙啶和 3-苯基-2H-氮丙啶的(nπ*)态开始的光化学裂解反应是超快的非绝热过程(<100 fs），通过 S1/S0 锥形交叉，生成腈叶立德。通过目前的动力学模拟，很好地再现了实验中叶立德的快速形成。对于 3-苯基-2H-氮丙啶，S1((1)ππ*)态的布居是 S2((1)nπ*)态的另一个衰减途径。光激发下 C-N 键的断裂通常被认为发生在 T1 态。然而，我们的计算表明，2-苯基-2H-氮丙啶的 C-N 单键光裂解很可能发生在 S1 态。本工作为 2H-氮丙啶及相关衍生物的光裂解机制提供了新的见解。
