An ab initio study of potentially aromatic and antiaromatic three-membered rings
An ab initio study of potentially aromatic and antiaromatic three-membered rings
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DOI：
10.1021/ja00010a009
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发表时间：
1991-05
影响因子：
15
通讯作者：
Y. Byun;S. Saebo;C. Pittman
中科院分区：
文献类型：
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作者：
Y. Byun;S. Saebo;C. Pittman
对18个三元环体系进行了从头算计算，其中包括11个闭壳体系和7个开壳体系。所有系统的几何结构都在RHF/6-31G**水平上进行了完全优化。已知和未知的闭壳分子包括环丙烯基阳离子，C3H3+，1，氮杂环阳离子，C2H2N+，2，二氮杂阳离子，CHN2+，3，三氮杂阳离子，N3+，4，及其非环异构体，硼烯，C2H3B，5，硼氮二烯，CH2Nb，6，硼二氮杂环，N2BH，7，氮杂二氮，Nb2H3，8，氮杂环阳离子，CHNb+，9，氮杂环烯，C2H3N，10，和双氮杂环阳离子，CH3H3+，11.所研究的开壳体系包括环丙烯基基，C3H3*，12，氮杂环基阳离子，C2H3N，+，13，双氮杂环基阳离子，CHNb+，14，11三氮杂环自由基阳离子，N3H*+，15，硼氮杂环自由基阳离子，CHNB*，16，氮杂二硼自由基阳离子，NB2H3，+，17，和二氮杂环氧自由基CH3N2*，18。这一系列包括潜在的芳香性和潜在的抗芳香性结构。根据价键共振杂化表示对优化结构进行了讨论。将以前的理论和实验结果与这些计算结果进行了比较。考虑了硼和氮在芳香族和非芳香族体系中的作用。发现了几个意想不到的结果。自由基14和16以及自由基阳离子13、15和17是感兴趣的，因为它们可能是具有三个Ir电子的体系。然而，13的氮杂环和15的三氮杂环的自由基阳离子都是非平面的，有两个电子。硼氮杂环自由基16和氮杂二硼环自由基阳离子17为平面结构。硼氮杂环自由基，16，是一个双电子体系，体系中未成对的电子主要位于硼上。17具有双电子芳香族体系，具有弱的BB键(近似于单电子键)和一定的BB Ir重叠。它的未配对电子也在轨道上。只有二氮杂基，14，被发现是一个三IR电子平面系统，尽管与该结构相关的任何抗芳香性。
Ab initio calculations were performed on 18 three-membered ring systems including 11 closed-shell and seven open-shell systems. The geometries of all systems were completely optimized on the RHF/6-31G** level. Both known and unknown closed-shell molecules were investigated including the cyclopropenyl cation, C3H3+, 1, the azirinyl cation, C2H2N+, 2, the diazirinyl cation, CHN2+, 3, the triazirinyl cation, N3+, 4, andits acyclic isomers, borirene, C2H3B, 5, borazirene, CH2NB, 6, boradiazirine, N2BH, 7, azadiboridine, NB2H3, 8, the borazarinyl cation, CHNB+, 9, azirene, C2H3N, 10, andthe diazaridinyl cation, CH3N2+, 11. Open-shell systems studied included the cyclopropenyl radical, C3H3*, 12, the azirinyl radical cation, C2H3N,+, 13, the diazirinyl radical, CHN2', 14, the triazirinyl radical cation, N3H*+, 15, the borazirinyl radical, CHNB*, 16, the azadiboridinyl radical cation, NB2H3,+, 17, andthe diaziridinyl radical CH3N2*, 18. This series includes both potentially aromatic and potentially antiaromatic structures. The optimized structures are discussed in terms of their valence bond resonance hybrid representations. Previous theoretical and experimental results are compared with these calculations. The effect of boron and nitrogen in aromatic and nonaromatic systems is considered. Several unforseen results were found. Radicals 14 and 16 and radical cations 13, 15, and 17 were of interest since they might be systems with three ir electrons. However, the azirinyl, 13, and triazirinyl, 15, radical cations were each nonplanar with two electrons. The borazirinyl radical, 16, and azadiboridinyl radical cation, 17, were planar. Borazirinyl radical, 16, is a two electron system with the unpaired electron in the system largely located at the boron. 17 has a two electron aromatic system with a weak BB bond (approximately a one-electron bond) with some BB ir overlap. Its unpaired electron is also in a orbital. Only the diazirinyl radical, 14, was found to be a three ir electron planar system in spite of any antiaromaticity associated with this structure.