Nucleophilic Aromatic Addition in Ionizing Environments: Observation and Analysis of New C–N Valence Bonds in Complexes between Naphthalene Radical Cation and Pyridine
Nucleophilic Aromatic Addition in Ionizing Environments: Observation and Analysis of New C–N Valence Bonds in Complexes between Naphthalene Radical Cation and Pyridine
复制标题
电离环境中的亲核芳香加成：萘自由基阳离子与吡啶络合物中新 C-N 价键的观察和分析
DOI：
10.1021/jacs.7b05756
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发表时间：
2017
影响因子：
15
通讯作者：
Head-Gordon, Martin
中科院分区：
文献类型：
--
作者：
Peverati, Roberto;Platt, Sean P.;Attah, Isaac K.;Aziz, Saaudallah G.;El-Shall, M. Samy;Head-Gordon, Martin
自由基有机离子可以通过类似于化学键的相互作用与中性有机物络合来稳定，但键能大大降低。这些相互作用是星际介质和太阳星云区域等电离环境中团簇生长和聚合反应的关键因素。使用质量选择离子淌度实验对萘 (Naph) 和吡啶 (Pyr) 之间的自由基阳离子络合物进行了表征。测得的Naph+·(Pyr)异二聚体的结合焓(20.9kcal/mol)超过Naph+·(Naph)同二聚体的结合焓(17.8kcal/mol)。在 Naph+•(Pyr) 异二聚体中添加 1-3 个吡啶分子可使结合焓增加 10-11 kcal/mol。通过电子结构计算对一系列丰富的 Naph+•(Pyr) 异构体进行了表征。计算出的 400 K 时的玻尔兹曼分布产生与实验相当一致的结合焓。全局最小值是由Pyr攻击Naph+·α-碳处形成的双子离子阳离子，将其杂化从sp2改变为扭曲的sp3。在氦气中测得的 Naph+•(Pyr) 异二聚体在 302 K 时的碰撞截面为 84.9 ± 2.5 Å2，与计算出的最低能量双张结构的角平均截面 (83.9–85.1 Å2 在 302 K) 非常吻合。通过能量分解分析可知，Naph+•(Pyr) 和 Bz+•(Pyr)（Bz 是苯）之间的结合能显着增加了 16 kcal/mol。从Naph+·(NH3)到Naph+·(Pyr)（以及Bz+·(NH3)和Bz+·(Pyr)之间）的结合的类似增加同样被合理化。
Radical organic ions can be stabilized by complexation with neutral organics via interactions that can resemble chemical bonds, but with much diminished bond energies. Those interactions are a key factor in cluster growth and polymerization reactions in ionizing environments such as regions of the interstellar medium and solar nebulae. Such radical cation complexes between naphthalene (Naph) and pyridine (Pyr) are characterized using mass-selected ion mobility experiments. The measured enthalpy of binding of the Naph+•(Pyr) heterodimer (20.9 kcal/mol) exceeds that of the Naph+•(Naph) homodimer (17.8 kcal/mol). The addition of 1–3 more pyridine molecules to the Naph+•(Pyr) heterodimer gives 10–11 kcal/mol increments in binding enthalpy. A rich array of Naph+•(Pyr) isomers are characterized by electronic structure calculations. The calculated Boltzmann distribution at 400 K yields an enthalpy of binding in reasonable agreement with experiment. The global minimum is a distonic cation formed by Pyr attack on Naph+•at the α-carbon, changing its hybridization from sp2to distorted sp3. The measured collision cross section in helium for the Naph+•(Pyr) heterodimer of 84.9 ± 2.5 Å2at 302 K agrees well with calculated angle-averaged cross sections (83.9–85.1 Å2at 302 K) of the lowest energy distonic structures. A remarkable 16 kcal/mol increase in the binding energy between Naph+•(Pyr) and Bz+•(Pyr) (Bz is benzene) is understood by energy decomposition analysis. A similar increase in binding from Naph+•(NH3) to Naph+•(Pyr) (as well as between Bz+•(NH3) and Bz+•(Pyr)) is likewise rationalized.