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Reversal of Clar's Aromatic-Sextet Rule in Ultrashort Single-End-Capped [5,5] Carbon Nanotubes.
ChemistryOpen ( IF 2.5 ) Pub Date : 2020-05-27 , DOI: 10.1002/open.202000091 Guglielmo Monaco 1 , Emeritus Lawrence T Scott 2 , Riccardo Zanasi 1
ChemistryOpen ( IF 2.5 ) Pub Date : 2020-05-27 , DOI: 10.1002/open.202000091 Guglielmo Monaco 1 , Emeritus Lawrence T Scott 2 , Riccardo Zanasi 1
Affiliation
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The three‐fold HOMO‐LUMO gap oscillation, typical of finite length armchair carbon nanotubes (CNT), has a major effect on the magnetic response of ultrashort, single‐end‐capped [5,5] carbon nanotubes to a perturbing magnetic field parallel to the main symmetry axis. For the CNT's containing 40, 70, and 100 carbon atoms, for which 100 % of the C=C double bonds can be grouped into aromatic‐sextets, i. e., fully or complete Clar networks, large paratropic (antiaromatic) global circulations around the cylindrical axis are predicted at the DFT level of calculation. Local and semi‐global diatropic (aromatic) currents of strengths not larger than that of the benzene molecule are determined for a perpendicular perturbing magnetic field. CNTs of intermediate lengths do not display this enhanced antiaromatic response. The paratropic current flow clearly shows that these complete Clar networks can be viewed as stacked cycloparaphenylene belts, each providing a double 
annulene circuit as a consequence of the quinoidal resonance structure that results from their closure. Paradoxically, the fully aromatic Clar structure itself is responsible for the enhanced global antiaromaticity.
中文翻译：
超短单端封端 [5,5] 碳纳米管中 Clar 芳香六重奏规则的逆转。
三重HOMO-LUMO间隙振荡是有限长度扶手椅碳纳米管（CNT）的典型特征，它对超短单端封端[5,5]碳纳米管对平行扰动磁场的磁响应有重大影响到主对称轴。对于含有 40、70 和 100 个碳原子的 CNT，其 100% 的 C=C 双键可分为芳香族六重组，即完全或完整的 Clar 网络，围绕圆柱体存在大的顺向（反芳香）全局环流轴是在 DFT 计算级别预测的。对于垂直扰动磁场，确定强度不大于苯分子的局部和半全局变异性（芳香族）电流。中等长度的碳纳米管不表现出这种增强的抗芳香反应。顺向电流清楚地表明，这些完整的 Clar 网络可以被视为堆叠的环对亚苯基带，每个带都提供双 轮烯电路是由于其闭合而产生的醌型共振结构的结果。矛盾的是，全芳香 Clar 结构本身就增强了整体反芳香性。
更新日期：2020-05-27
annulene circuit as a consequence of the quinoidal resonance structure that results from their closure. Paradoxically, the fully aromatic Clar structure itself is responsible for the enhanced global antiaromaticity.
中文翻译：
超短单端封端 [5,5] 碳纳米管中 Clar 芳香六重奏规则的逆转。
三重HOMO-LUMO间隙振荡是有限长度扶手椅碳纳米管（CNT）的典型特征，它对超短单端封端[5,5]碳纳米管对平行扰动磁场的磁响应有重大影响到主对称轴。对于含有 40、70 和 100 个碳原子的 CNT，其 100% 的 C=C 双键可分为芳香族六重组，即完全或完整的 Clar 网络，围绕圆柱体存在大的顺向（反芳香）全局环流轴是在 DFT 计算级别预测的。对于垂直扰动磁场，确定强度不大于苯分子的局部和半全局变异性（芳香族）电流。中等长度的碳纳米管不表现出这种增强的抗芳香反应。顺向电流清楚地表明，这些完整的 Clar 网络可以被视为堆叠的环对亚苯基带，每个带都提供双
轮烯电路是由于其闭合而产生的醌型共振结构的结果。矛盾的是，全芳香 Clar 结构本身就增强了整体反芳香性。
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