Molecular models of benzene and selected polycyclic aromatic hydrocarbons in the aqueous and adsorbed states
Molecular models of benzene and selected polycyclic aromatic hydrocarbons in the aqueous and adsorbed states
复制标题
苯和选定的多环芳烃在水态和吸附态的分子模型
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
S. Apitz
中科院分区：
文献类型：
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作者：
J. Kubicki;G. Blake;S. Apitz
采用半经验、从头算Hartree-Fock和密度泛函3种不同的分子模拟方法，计算了一系列常见多环芳烃（PAHs）在气相中的最高占据分子轨道与最低未占据分子轨道之间的能隙（Δ EHOMO-LUMO）.结果表明，半经验，Hartree-Fock和密度泛函计算可以提供有用的相对HOMO-LUMO间隙信息，但这些方法高估了实际的Δ EHOMO-LUMO。基于振动频率分析，密度泛函计算可靠地产生动态稳定的结构，可用于预测模型Δ EHOMO-LUMO值。半经验和从头算Hartree-Fock方法在预测动态稳定结构方面都不可靠;因此，对于几种PAHs，Δ EHOMO-LUMO值的预测是不可能的。采用自洽反应场方法和显式溶剂化方法计算了苯和选定多环芳烃由于溶剂化效应引起的HOMO-LUMO能隙的变化。模拟水和辛醇溶剂化的自洽等密度极化连续模型计算不会改变计算的Δ EHOMO-LUMO值，足以影响预测的光毒性;因此，气相值可用于溶液和体内的PAH。PAH键合到矿物表面基团的能量学也被建模。在某些情况下，多环芳烃与模型铝酸盐表面缺陷的相互作用表明，Δ EHOMO-LUMO值可能会因吸附而显著降低，这将降低化学稳定性。未预测会增加化合物化学稳定性的Δ EHOMO-LUMO计算值显著增加。
Energy gaps between the highest‐occupied molecular orbital and lowest‐unoccupied molecular orbital (ΔEHOMO‐LUMO) for a suite of common polycyclic aromatic hydrocarbons (PAHs) in the gas‐phase were calculated with three different molecular modeling methods: semiempirical, ab initio Hartree‐Fock, and density functional calculations. Results indicate that semiempirical, Hartree‐Fock, and density functional calculations may provide useful relative HOMO‐LUMO gap information, but these methods overestimate the actual ΔEHOMO‐LUMO. Based on vibrational frequency analyses, density functional calculations reliably produce dynamically stable structures that can be used to predict model ΔEHOMO‐LUMO values. Both the semiempirical and ab initio Hartree‐Fock methods were unreliable in predicting dynamically stable structures; hence prediction of ΔEHOMO‐LUMO values was not possible for several PAHs. Changes in the HOMO‐LUMO gap of benzene and selected PAHs due to solvation effects were calculated using self‐consistent reaction field methods and explicit solvation. Self‐consistent isodensity polarized continuum model calculations modeling water and octanol solvation do not change calculated ΔEHOMO‐LUMO values enough to affect predicted phototoxicities; thus, gas‐phase values may be used for PAHs in solution and in vivo. Energetics of PAH bonding to mineral surface groups were also modeled. In some cases, interaction of PAHs with model aluminate surface defects suggests that ΔEHOMO‐LUMO values may be lowered significantly by adsorption that would lower chemical stabilities. Significant increases in calculated ΔEHOMO‐LUMO that would increase chemical stability of the compounds were not predicted.