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Interplay of Aromaticity and Antiaromaticity in N-Doped Nanographenes.
The Journal of Physical Chemistry A ( IF 2.9 ) Pub Date : 2020-01-22 , DOI: 10.1021/acs.jpca.9b11315
Isaac Benkyi 1 , Olga Staszewska-Krajewska 2 , Daniel T Gryko 2 , Michał Jaszuński 2 , Amnon Stanger 3 , Dage Sundholm 1
Affiliation  

The aromaticity of three nonplanar, fully conjugated aza-nanographenes built around a pyrrolo[3,2-b]pyrrole core is assessed through the application of two different computational procedures-GIMIC and NICS. We examine the calculated magnetically induced current densities (GIMIC) and nucleus-independent chemical shifts (NICS). The structural differences between these three apparently similar molecules lead to significantly different aromatic properties. GIMIC analysis indicates that the peripheral diatropic ring current of 3.9 nA/T for the studied bowl-shaped diaza-nanographene is the strongest, followed by the double [6]helicene which lacks seven-membered rings, and is practically nonexistent for the double [5]helicene possessing seven-membered rings. The biggest difference however is that in the two not-fully-fused molecules, the central pyrrole rings possess a significant diatropic current of about 4.1 nA/T, whereas there is no such current in the diaza-nanographene. Moreover, the antiaromaticity of the seven-membered rings is increasing while moving from double [5]helicene to diaza-nanographene (from -2.4 to -6.0 nA/T). The induced currents derived from NICSπ,zz-XY-scan analysis for all of the studied systems are in qualitative agreement with the GIMIC results. Subtle differences may originate from σ-electron currents in GIMIC or inaccuracy of NICSπ,zz values due to the nonplanarity of the systems, but the general picture is similar.

中文翻译:

N掺杂纳米石墨烯中芳香性和抗芳香性的相互作用。

通过应用两种不同的计算程序-GIMIC和NICS,评估了围绕吡咯并[3,2-b]吡咯核构建的三种非平面,完全共轭的氮杂-纳米碳烯的芳香性。我们检查了计算出的磁感应电流密度(GIMIC)和独立于核的化学位移(NICS)。这三个表面上相似的分子之间的结构差异导致显着不同的芳族特性。GIMIC分析表明,所研究的碗状重氮-纳米碳烯的环变径三环电流为3.9 nA / T最强,其次是缺乏七元环的双[6]螺旋,而双[6]螺旋几乎不存在。 5] hel烯具有七元环。但是最大的区别是,在两个未完全融合的分子中,中心的吡咯环具有显着的变径电流,约为4.1 nA / T,而在diaza-nanographene中没有这样的电流。此外,七元环的抗芳香性在从双[5]螺旋烯转变为重氮-纳米碳烯(从-2.4到-6.0 nA / T)时增加。从NICSπ,zz-XY扫描分析得出的所有研究系统的感应电流与GIMIC结果定性一致。微弱的差异可能是由于GIMIC中的σ电子电流或由于系统的非平面性而导致的NICSπ,zz值的不准确引起的,但总体情况是相似的。当从双[5]螺旋烯向diaza-nanographene(从-2.4到-6.0 nA / T)移动时,七元环的抗芳香性增加。从NICSπ,zz-XY扫描分析得出的所有研究系统的感应电流与GIMIC结果定性一致。微弱的差异可能是由于GIMIC中的σ电子电流或由于系统的非平面性而导致的NICSπ,zz值的不准确引起的,但总体情况是相似的。当从双[5]螺旋烯向diaza-nanographene(从-2.4到-6.0 nA / T)移动时,七元环的抗芳香性增加。从NICSπ,zz-XY扫描分析得出的所有研究系统的感应电流与GIMIC结果定性一致。微弱的差异可能是由于GIMIC中的σ电子电流或由于系统的非平面性而导致的NICSπ,zz值的不准确引起的,但总体情况是相似的。
更新日期:2020-01-23
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