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Local aromaticity in polyacenes manifested by individual proton and carbon shieldings: DFT mapping of aromaticity
Magnetic Resonance in Chemistry ( IF 2 ) Pub Date : 2019-11-21 , DOI: 10.1002/mrc.4967
Magdalena Gajda 1 , Łukasz Gajda 2 , Teobald Kupka 2 , Tapas Kar 3
Affiliation  

Exponential dependencies between locally calculated geometric and magnetic indexes of aromaticity, harmonic oscillator model of aromaticity (HOMA) and nucleus independent chemical shifts (NICS)(0), NICS(1) and NICS(1)zz, and the number of conjugated benzene rings in linear acenes, from benzene to decacene were observed at B3LYP/6‐311+G** level of theory. Correlations between HOMA and NICS indexes showed exponential dependencies and were fitted with simple three‐parameter function. Similar correlations between both indexes of aromaticity and proton and carbon nuclear isotropic shieldings of individual acene rings were observed. Contrary to proton data, the predicted 13C nuclear isotropic shieldings of carbon atoms belonging to inner rings in polyacenes were less shielded, indicating lower aromaticity and therefore, higher reactivity.

中文翻译:

由单个质子和碳屏蔽表现出的多并苯的局部芳香性:芳香性的 DFT 映射

局部计算的芳香性几何和磁性指数、芳香性谐振子模型 (HOMA) 和核独立化学位移 (NICS)(0)、NICS(1) 和 NICS(1)zz 以及共轭苯环数量之间的指数相关性在线性并苯中,在 B3LYP/6-311+G** 理论水平观察到从苯到癸苯。HOMA 和 NICS 指数之间的相关性显示出指数相关性,并用简单的三参数函数拟合。观察到芳香性指标与单个并苯环的质子和碳核各向同性屏蔽之间的相似相关性。与质子数据相反,属于多并苯内环的碳原子的预测 13C 核各向同性屏蔽较少,表明芳香性较低,因此反应性较高。
更新日期:2019-11-21
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