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<p>The present work reports a Density Functional Theory (DFT)-based computational investigation into the question of aromaticity of azaborines (1,2-azaborine, 1,3-azaborine and 1,4-azaborine). The aromaticity of the molecules has been addressed by the method of Nucleus-Independent Chemical Shift (NICS) scan which reveals the presence of diatropic ring current within the rings revealing the trend of aromaticity as: benzene &gt; 1,3-azaborine &gt; 1,2-azaborine ≈ 1,4-azaborine &gt; borazine. The test of aromaticity based on Harmonic Oscillator Model of Aromaticity (HOMA) index shows a trend as: benzene &gt; borazine &gt; 1,3-azaborine ≈ 1,2-azaborine &gt; 1,4-azaborine, whereas the electronic-based aromaticity indices like <i>para</i>-delocalization index (PDI), <i>para</i>-linear response (PLR) index and multi-center delocalization index (MCI) shows a trend as: benzene &gt; 1,3-azaborine ≈ 1,2-azaborine &gt; 1,4-azaborine &gt; borazine. The trend predicted by aromatic fluctuation (FLU) index (benzene &gt; borazine &gt; 1,3-azaborine &gt; 1,2-azaborine &gt; 1,4-azaborine), or the energetic criterion of aromatic stabilization energy (1,3-azaborine &gt; benzene &gt; 1,2-azaborine ≈ 1,4-azaborine &gt; borazine) is found to vary from those of the other criteria. All the aromaticity indices of azaborines are systematically compared with the hydrocarbon (benzene) and fully B-N (borazine) parents. Though the results indicate the aromatic character of the molecules, distinct discrepancies are noted in predicting the trend of aromaticity whereby pointing toward the ambiguity that still persists in calculation of the important qualitative phenomenon of aromaticity in azaborines.</p> Graphical Abstract <p>A Density Functional Theory-based computational investigation into the question of aromaticity of 1,2-, 1,3- and 1,4-azaborines with reference to magnetic, energetic, geometrical and electronic-based criteria is undertaken. Through systematic comparison with the hydrocarbon (benzene) and fully B-N (borazine) parents the discrepancies among various aromaticity indices are highlighted.</p> <p></p>

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Aromaticity of Azaborines: Discrepancies Among Various Aromaticity Indices

  • 期刊论文

  • 发表日期：

    2026年5月11日

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  • Bijan K. Paul

摘要

The present work reports a Density Functional Theory (DFT)-based computational investigation into the question of aromaticity of azaborines (1,2-azaborine, 1,3-azaborine and 1,4-azaborine). The aromaticity of the molecules has been addressed by the method of Nucleus-Independent Chemical Shift (NICS) scan which reveals the presence of diatropic ring current within the rings revealing the trend of aromaticity as: benzene > 1,3-azaborine > 1,2-azaborine ≈ 1,4-azaborine > borazine. The test of aromaticity based on Harmonic Oscillator Model of Aromaticity (HOMA) index shows a trend as: benzene > borazine > 1,3-azaborine ≈ 1,2-azaborine > 1,4-azaborine, whereas the electronic-based aromaticity indices like para-delocalization index (PDI), para-linear response (PLR) index and multi-center delocalization index (MCI) shows a trend as: benzene > 1,3-azaborine ≈ 1,2-azaborine > 1,4-azaborine > borazine. The trend predicted by aromatic fluctuation (FLU) index (benzene > borazine > 1,3-azaborine > 1,2-azaborine > 1,4-azaborine), or the energetic criterion of aromatic stabilization energy (1,3-azaborine > benzene > 1,2-azaborine ≈ 1,4-azaborine > borazine) is found to vary from those of the other criteria. All the aromaticity indices of azaborines are systematically compared with the hydrocarbon (benzene) and fully B-N (borazine) parents. Though the results indicate the aromatic character of the molecules, distinct discrepancies are noted in predicting the trend of aromaticity whereby pointing toward the ambiguity that still persists in calculation of the important qualitative phenomenon of aromaticity in azaborines.

Graphical Abstract

A Density Functional Theory-based computational investigation into the question of aromaticity of 1,2-, 1,3- and 1,4-azaborines with reference to magnetic, energetic, geometrical and electronic-based criteria is undertaken. Through systematic comparison with the hydrocarbon (benzene) and fully B-N (borazine) parents the discrepancies among various aromaticity indices are highlighted.