The N‐heterocyclic carbene, imidazole‐2‐ylidene, and its main group (13‐15) analogues contain cyclically conjugated 6π electrons. Experimental ¹H nuclear magnetic resonance (NMR) spectra suggest an increase in aromaticity along a period from left to right. Whereas the order along a group is as follows: period 2 > period 5 > period 4 > period 3 due to change in structure. To understand the order of aromaticity, the magnetically induced ring currents of the molecules are calculated using aromatic ring current shielding, gauge‐including magnetically induced currents (GIMIC) method and Stanger's σ‐model applying the gauge‐including atomic orbitals NMR technique. It is found that GIMIC best describes the order of aromaticity especially along a group where current‐profile changes on the bivalent atom down a group due to change in electron density. Moreover, the GIMIC provides the visualization of current by sign modulus and the anisotropy of the induced current density plots.

中文翻译：

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N-杂环卡宾及其类似物的芳香性：磁感应环电流的观点

N-杂环卡宾，咪唑-2-亚基及其主要的基团（13-15）类似物包含循环共轭6π电子。实验¹H核磁共振（NMR）光谱表明，从左到右的一段时间内，芳香性增加。而沿着组的顺序如下：由于结构变化，周期2>周期5>周期4>周期3。为了理解芳香性的顺序，使用芳香环电流屏蔽，量规（包括磁感应电流）（GIMIC）方法和应用量规（包括原子轨道NMR）的Stangerσ模型来计算分子的磁感应环电流。发现GIMIC最好地描述了芳香性的顺序，尤其是在由于电子密度变化导致电流分布在二价原子上向下变化的基团上。此外，GIMIC通过符号模量和感应电流密度图的各向异性提供了可视化的电流。