School of Chemistry and ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, NSW 2006, Australia.
J Phys Chem A. 2013 Feb 28;117(8):1834-42. doi: 10.1021/jp312585r. Epub 2013 Jan 23.
In this study, we address the issues associated with predicting usefully accurate heats of formation for moderately-sized molecules such as corannulene and C(60). We obtain a high-level theoretical heat of formation for corannulene through the use of reaction schemes that conserve increasingly larger molecular fragments between the reactants and products. The reaction enthalpies are obtained by means of the high-level, ab initio W1h thermochemical protocol, while accurate experimental enthalpies of formation for the other molecules involved in the reactions are obtained from the Active Thermochemical Tables (ATcT) network. Our best theoretical heat of formation for corannulene (Δ(f)H°(298)[C(20)H(10)(g)] = 485.2 ± 7.9 kJ mol(-1)) differs significantly from the currently accepted experimental value (Δ(f)H°(298)[C(20)H(10)(g)] = 458.5 ± 9.2 kJ mol(-1)), and this suggests that re-examination of the experimental data may be in order. We have used our theoretical heat of formation for corannulene to obtain a predicted heat of formation of C(60) through reactions that involve only corannulene and planar polyacenes. Current experimental values span a range of ~200 kJ mol(-1). Our reaction enthalpies are obtained by means of double-hybrid density functional theory in conjunction with a large quadruple-ζ basis set, while accurate experimental heats of formation (or our theoretical value in the case of corannulene) are used for the other molecules involved. Our best theoretical heat of formation for C(60) (Δ(f)H°(298)[C(60)(g)] = 2521.6 kJ mol(-1)) suggests that the experimental value adopted by the NIST thermochemical database (Δ(f)H°(298)[C(60)(g)] = 2560 ± 100 kJ mol(-1)) should be revised downward.
在这项研究中，我们解决了与预测中等大小分子（如苝和 C(60)）有用准确生成热相关的问题。我们通过使用反应物和产物之间保持越来越大的分子片段的反应方案来获得苝的高水平理论生成热。反应焓通过高水平的从头算 W1h 热化学方案获得，而参与反应的其他分子的准确实验生成热则从活性热化学表（ATcT）网络获得。我们对苝的最佳理论生成热（Δ(f)H°(298)[C(20)H(10)(g)] = 485.2 ± 7.9 kJ mol(-1)）与目前公认的实验值（Δ(f)H°(298)[C(20)H(10)(g)] = 458.5 ± 9.2 kJ mol(-1)）有很大的差异，这表明可能需要重新检查实验数据。我们已经使用苝的理论生成热来通过仅涉及苝和平面多环芳烃的反应来获得 C(60)的预测生成热。目前的实验值在~200 kJ mol(-1)范围内。我们的反应焓通过双杂交密度泛函理论与大四重ζ基组结合获得，而其他分子则使用准确的实验生成热（或苝的理论值）。我们对 C(60)的最佳理论生成热（Δ(f)H°(298)[C(60)(g)] = 2521.6 kJ mol(-1)）表明，NIST 热化学数据库采用的实验值（Δ(f)H°(298)[C(60)(g)] = 2560 ± 100 kJ mol(-1)）应向下修正。
