The resonance energy of benzene: a revisit.
The resonance energy of benzene: a revisit.
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DOI：
10.1021/jp808941h
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发表时间：
2009-03
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影响因子：
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通讯作者：
Y. Mo
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文献类型：
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作者：
Y. Mo
Zielinski和货车Lenthe最近通过引入共振BLW（RBLW）方法扩展了块局域波函数（BLW）方法，并对六方H（6）和苯进行了测试计算[J. Phys. Chem. A 2008，112，13197]。然而，鲍林的共振能从他们的RBLW和从头计算价键（VB）计算大大低估了主要是由于不完善的使用单电子轨道（方法=离域）或共振结构（方法=本地）。虽然人们已经很好地认识到，在分子系统中的电子共振起着稳定的作用，有许多间接的实验证据可用于评估共振能量，从而证明计算结果。在这里，我们使用了BLW方法，这可以被视为现代从头算VB理论的最简单的变体，重新评估苯的共振能在B3 LYP水平，以下由Pauling和Wheland，谁获得的共振能的原始定义“通过减去的实际能量的分子的问题，从最稳定的贡献结构”。计算的垂直共振能量苯中的绝热共振能（或量子力学共振能）分别为88.8、92.2或87.9 kcal/mol，基组分别为6- 31 G（d）、6-311+G（d，p）或cc-pVTZ，而绝热共振能（或量子力学共振能）分别为88.8、92.2或87.9 kcal/mol。4、63.2或62.4kcal/mol，对于中等基组表现出不显著的基组依赖性。与预测一致，难以捉摸的环己三烯（即，Kekule结构）也导致碳-碳键长（例如，1.322和1.523 A，具有cc-pVTZ基组），与乙烯或乙烷中的那些相当。
Zielinski and van Lenthe recently extended the block-localized wave function (BLW) method by introducing the resonating BLW (RBLW) method and performed test calculations on hexagonal H(6) and benzene [J. Phys. Chem. A 2008, 112, 13197]. However, the Pauling's resonance energies from their RBLW and ab initio valence bond (VB) calculations were greatly underestimated largely due to the imperfect use of either one-electron orbitals (method = delocal) or resonance structures (method = local). Whereas it has been well recognized that electronic resonance within a molecular system plays a stabilizing role, there are many indirect experimental evidences available to evaluate the resonance energy and, thus, to justify computational results. Here we used the BLW method, which can be regarded as the simplest variant of modern ab initio VB theory, to re-evaluate the resonance energy of benzene at the B3LYP level, following the original definition by Pauling and Wheland, who obtained the resonance energy "by subtracting the actual energy of the molecule in question from that of the most stable contributing structure". The computed vertical resonance energy (or quantum mechanical resonance energy) in benzene is 88.8, 92.2, or 87.9 kcal/mol with the basis sets of 6-31G(d), 6-311+G(d,p), or cc-pVTZ, respectively, while the adiabatic resonance energy (or theoretical resonance energy) is 61.4, 63.2, or 62.4 kcal/mol, exhibiting insignificant basis set dependency for moderate basis sets. In line with predictions, the geometry optimization of the elusive cyclohexatriene (i.e., the Kekule structure) with the BLW method also resulted in carbon-carbon bond lengths (e.g., 1.322 and 1.523 A with the cc-pVTZ basis set) comparable to those in ethylene or ethane.