Periodoannulenes: A Generalized Annulene-within-an-Annulene Paradigm for Combined σ and π Ring Currents,The Journal of Physical Chemistry A

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Periodoannulenes: A Generalized Annulene-within-an-Annulene Paradigm for Combined σ and π Ring Currents
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2021-07-19 , DOI: 10.1021/acs.jpca.1c03170
Patrick W Fowler ₁ , Remco W A Havenith _{2,

3}

Affiliation

Periodoannulene molecules and ions C_xI_x^q in planar geometry offer examples of systems with the potential for outer σ and inner π ring-current double aromaticity, given a sufficient overlap of tangential p_σ-orbital manifolds on the large atoms of the outer cycle. Previous theoretical work indicated concentric diatropic currents in the dication C₆I₆²⁺. Ab initio ipsocentric calculations support an account in terms of frontier-orbital selection rules for current contributions in C₆I₆²⁺ (and radical C₆I₆⁺, implicated in recent experimental work on the oxidation of periodobenzene). A σ/π analogue of the annulene-within-an-annulene model is applied here to periodo systems based on cyclooctatetraene. Model species C₈I₈^q with charges q = 0, +1, +2, +4, −2 and structures constrained to a planar D_4h symmetry exhibit maps with all combinations of σ/π con- and counter-rotation, comprising global σ ring currents on the iodine perimeter and central π ring currents on the carbocycle. All can be rationalized by the separate application of the tropicity selection rules to the two subsystems, whether in singlet or triplet states.

中文翻译：

周期环烯：用于组合 σ 和 π 环电流的广义环环内环流范式

平面几何中的每碘环分子和离子 C _x I _x^q提供了具有外 σ 和内 π 环电流双芳香性潜力的系统示例，前提是外层大原子上的切向 p _σ轨道流形有足够的重叠循环。先前的理论工作表明在双方向 C ₆ I ₆^{2+ 中}存在同心双向性电流。从头算同心计算支持 C ₆ I ₆²⁺（和激进 C ₆ I ₆^+）中当前贡献的前沿轨道选择规则，牵连在最近的实验工作，对氧化每碘苯）。环中环模型的 σ/π 类似物在此应用于基于环辛四烯的每碘系统。模型物种 C ₈ I ₈^q带有电荷q = 0, +1, +2, +4, -2 并且结构被约束到平面D _{4 h}对称性展示了具有 σ/π 旋转和反向旋转的所有组合的映射，包括碘周边上的全局 σ 环电流和碳环上的中心 π 环电流。所有这些都可以通过将热带选择规则单独应用于两个子系统来合理化，无论是单线态还是三线态。

更新日期：2021-07-29

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