Reactivity and regioselectivity in Diels-Alder reactions of anion encapsulated fullerenes
Reactivity and regioselectivity in Diels-Alder reactions of anion encapsulated fullerenes
复制标题
阴离子封装富勒烯的 Diels-Alder 反应的反应性和区域选择性
DOI：
10.1039/c7cp06365b
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发表时间：
2017-12-07
影响因子：
3.3
通讯作者：
Lan, Yu
中科院分区：
文献类型：
--
作者：
Cui, Cheng-Xing;Zhang, Zhao-Pei;Lan, Yu
包封和表面化学改性是提高富勒烯性能的方法，用于各种应用。本文中，进行密度泛函理论计算以研究阴离子包封的C-60（包括[X@C-60]（-）（X = F、Cl、Br或I）、[S@C-60]（2-）和[N@C-60]（3-））的Diels-Alder（DA）反应性。计算结果表明，封装的Cl-，Br-，I-，或S2-阴离子位于靠近C-60分子的中心，然而，封装的F-从中心被取代。碳笼的内表面被包裹的N3-键，这导致负电荷转移到C-60。在[N@C-60]（3-）中，靠近被包裹的N原子的C-C键反应性更强。我们的计算表明，封装卤素或S阴离子降低DA反应性，因为封装的阴离子更强的闭壳排斥。然而，封装的N3-增加DA反应性。卤素-或S2-阴离子包封的C-60的较高的畸变能导致6-5键的较低的反应性。DA与[N@C-60]（3-）反应的相反区域选择性归因于环戊二烯（CPD）部分的畸变能。不对称的过渡态几何结构导致CPD部分的较低的畸变能。
Encapsulation and surface chemical modification are methodologies to enhance the properties of fullerenes for various applications. Herein, density functional theory calculations are performed to study the Diels-Alder (DA) reactivity of anion encapsulated C-60, including [X@C-60](-) (X = F, Cl, Br, or I), [S@C-60](2-), and [N@C-60](3-). Computational results reveal that encapsulated Cl-, Br-, I-, or S2- anions are located close to the center of the C-60 molecule; however, encapsulated F- is displaced from the center. Encapsulated N3- bonds to the inner surface of the carbon cage, which leads to a negative charge transfer to the C-60. In [N@C-60](3-), C-C bonds near to the encapsulated N atom are more reactive. Our calculations reveal that encapsulated halogen or S anions decrease the DA reactivity because of the stronger closed-shell repulsion of the encapsulated anion. However, encapsulated N3- increases the DA reactivity. The higher distortion energy of the halogen- or S2--anion encapsulated C-60 leads to lower reactivity of the 6-5 bond. Opposite regioselectivity of the DA reaction with [N@C-60](3-) is attributed to distortion energy of the cyclopentadiene (CPD) moiety. The asymmetrical transition state geometry leads to a lower distortion energy of the CPD moiety.