Institute of Chemistry, The Edmond Safra Campus, Givat Ram, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
Phys Chem Chem Phys. 2012 Jul 7;14(25):8836-41. doi: 10.1039/c2cp23849g. Epub 2012 Feb 15.
The photochemistry of the pyrrole-ammonia cluster is analyzed theoretically. Whereas in neat pyrrole the dominant photochemical reaction is H-atom cleavage, recent experiments show that in pyrrole-ammonia clusters the major reaction is H-transfer to form the NH(4) radical (solvated by ammonia molecules in the case of large clusters) and the pyrrolyl radical. A mechanism involving the hydrogen-bonded Rydberg state is offered to account for these results and verified computationally. Two minima are located on the lowest excited singlet PES. Both of them are Rydberg states, one leads to the formation of NH(4) and pyrrolyl radicals, the other is connected to the πσ* state through a relatively high barrier, leading to a 3-body dissociation reaction to form a pyrrolyl radical, ammonia and an H-atom. The former is the energetically and statistically preferred one.
吡咯-氨簇的光化学性质通过理论进行了分析。虽然在纯吡咯中，主要的光化学反应是氢原子的断裂，但最近的实验表明，在吡咯-氨簇中，主要的反应是氢转移，形成 NH4 自由基（在大簇的情况下被氨分子溶剂化）和吡咯基自由基。提出了一种涉及氢键的里德堡态的机制来解释这些结果，并通过计算进行了验证。在最低激发 singlet PES 上找到了两个最小值。它们都是里德堡态，一个导致 NH4 和吡咯基自由基的形成，另一个通过相对较高的势垒与 πσ*态相连，导致三体解离反应，形成吡咯基自由基、氨和一个 H 原子。前者在能量和统计上是首选的。
