Effect on Ring Current of the Kekule Vibration in Aromatic and Antiaromatic Rings
Effect on Ring Current of the Kekule Vibration in Aromatic and Antiaromatic Rings
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DOI：
10.1021/jp2077424
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发表时间：
2011-11-24
影响因子：
2.9
通讯作者：
Fowler, Patrick W.
中科院分区：
文献类型：
--
作者：
Bean, David E.;Fowler, Patrick W.
导数电流密度图被用来跟踪环电流的变化(因此，在磁性标准下，芳香性的变化)与典型的芳香族、抗芳香族和非芳香族体系的凯库勒振动，环辛四烯(COT)和冰片。MAP按同心CHF/6-31G**//RHF/6-31G**水平计算。苯的一阶导数图显示了局域键电流的增长，而二阶导数图显示了一个纯的、顺向的“反环电流”，从而得出了沿着Kekule模式的振动运动将平均降低苯的净芳香性的结论。对于平面约束的D-4H胶辊，Kekule模式(键长交替减少的正值)增加了一阶和二阶的对立性，表明沿该模式零点运动的抗芳香性平均增加。在环电流判据下，苯和D-4H胶辊的呼吸膨胀分别降低了芳香性和增加了抗芳香性。
Derivative current-density maps are used to follow the changes in ring-current (and hence, on the magnetic criterion, the changes in aromaticity) with the Kekule vibrations of the prototypical aromatic, antiaromatic, and nonaromatic systems of benzene, cyclooctatetraene (COT), and borazine. Maps are computed at the ipsocentric CHF/6-31G**//RHF/6-31G** level. The first-derivative map for benzene shows a growing-in of localized bond currents, and the second-derivative map shows a pure, paratropic "antiring-current", leading to the conclusion that vibrational motion along the Kekule mode will reduce the net aromaticity of benzene, on average. For planar-constrained D-4h COT, the Kekule mode (positive for reduction of bond-length alternation) increases paratropicity at both first and second order, indicating an average increase in antiaromaticity with zero-point motion along this mode. On the ring-current criterion, breathing expansions of benzene and D-4h COT reduce aromaticity and increase antiaromaticity, respectively.