Nucleus-independent chemical shifts and local aromaticities in large polycyclic aromatic hydrocarbons
Nucleus-independent chemical shifts and local aromaticities in large polycyclic aromatic hydrocarbons
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DOI：
10.1016/s0009-2614(02)01415-x
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发表时间：
2002-10-28
影响因子：
2.8
通讯作者：
Aihara, J
中科院分区：
文献类型：
--
作者：
Aihara, J
晕苯和克库勒烯的中心环虽然是（4 n + 2）元环，但都具有很小的正核独立化学位移（NICS）值，是一种具有倒向性的中心环。然而，仔细检查每个π系统中的键共振能（BRE）模式发现，所有组成环本质上都是芳香族的。个别环被发现，以维持diatropic电流，即使一些债券电流是消失的小。因此，在大型多环IT系统（包括富勒烯）的环中心的NICS值不能总是用作局部芳香性的指标。BRE更适合于估计多环it-体系的局部芳香性程度。(C)2002 Elsevier Science B. V.保留所有权利。
Central rings of coronene and kekulene are known to be paratropic with small positive nucleus-indepedent chemical shift (NICS) values at the centers although they are (4n + 2)-membered rings. However, careful inspection of the bond resonance energy (BRE) pattern in each pi-system revealed that all constituent rings are aromatic in nature. Individual rings were found to sustain diatropic currents even if some bond currents are vanishingly small. Thus, NICS values at the ring centers of large polycyclic it-systems, including fullerenes, cannot always be used as indicators of local aromaticity. BRE is better suited for estimating the degree of local aromaticity in polycyclic it-systems. (C) 2002 Elsevier Science B.V. All rights reserved.