Arene-cation interactions of positive quadrupole moment aromatics and arene-anion interactions of negative quadrupole moment aromatics
Arene-cation interactions of positive quadrupole moment aromatics and arene-anion interactions of negative quadrupole moment aromatics
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DOI：
10.1021/jp065175v
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发表时间：
2006-11-23
影响因子：
2.9
通讯作者：
Lewis, Michael
中科院分区：
文献类型：
--
作者：
Clements, Aimee;Lewis, Michael
涉及芳香族π电子密度的分子间相互作用被广泛认为由芳香族分子四极矩Theta（zz）控制。芳烃-阳离子结合被认为主要发生在负Theta（zz）芳烃中，芳烃-阴离子结合被认为主要发生在正Theta（zz）芳烃中。我们已经进行了量子力学计算，表明正Theta（zz）芳烃的阳离子结合和负Theta（zz）芳烃的阴离子结合在气相中是相当常见的。六氟苯的π电子密度，原型正Theta（zz）芳族化合物（实验Theta（zz）= +9.5 +/-0.5 D埃），在MP2（全）/6- 311 G ** 理论水平下具有-4.37 kcal/mol的Li+结合焓。RHF/6- 311 G ** 计算的1，4-二氰基苯的Theta（zz）值为+11.81 D埃，但其MP2（全）/6- 311 G **Li+结合焓为-12.65 kcal/mol，Na+结合焓为-3.72 kcal/mol。苯（原型负Theta（zz）芳族化合物（实验Theta（zz）= -8.7 +/-0.5 D埃））的π电子密度具有-5.51 kcal/mol的F结合焓。C6 H2 I4的RHF/6- 311 G ** 计算的Theta（zz）为-10.45 D埃，但其具有-20.13 kcal/mol的MP2（全）/6-311++G** 计算的F-结合焓。我们的结果表明，随着芳香族Theta（zz）值的增加，阳离子结合焓降低;阳离子结合焓与芳香族Theta（zz）的关系图给出了最佳拟合线，R-2 = 0.778。芳香族Theta（zz）值和阴离子结合焓之间不存在这种相关性;最佳拟合线具有R-2 = 0.297。这些结果进行了讨论，在静电和极化率的贡献，整体结合hapropies。
Intermolecular interactions involving aromatic pi-electron density are widely believed to be governed by the aromatic molecular quadrupole moment, Theta(zz). Arene-cation binding is believed to occur primarily with negative Theta(zz) aromatics, and arene-anion binding is believed to occur largely with positive Theta(zz) aromatics. We have performed quantum mechanical computations that show the cation binding of positive Theta(zz) aromatics and the anion binding of negative Theta(zz) aromatics is quite common in the gas phase. The pi-electron density of hexafluorobenzene, the prototypical positive Theta(zz) aromatic (experimental Theta(zz) = +9.5 +/- 0.5 D angstrom), has a Li+ binding enthalpy of -4.37 kcal/mol at the MP2(full)/6-311G** level of theory. The RHF/6-311G** calculated Theta(zz) value of 1,4-dicyanobenzene is +11.81 D angstrom, yet it has an MP2(full)/6-311G**Li+ binding enthalpy of -12.65 kcal/mol and a Na+ binding enthalpy of -3.72 kcal/mol. The pi-electron density of benzene, the prototypical negative Theta(zz) aromatic (experimental Theta(zz) = -8.7 +/- 0.5 D angstrom), has a F- binding enthalpy of -5.51 kcal/mol. The RHF/6-311G** calculated Theta(zz) of C6H2I4 is -10.45 D angstrom, yet it has an MP2(full)/6-311++G** calculated F- binding enthalpy of -20.13 kcal/mol. Our results show that as the aromatic Theta(zz) value increases the cation binding enthalpy decreases; a plot of cation binding enthalpies versus aromatic Theta(zz) gives a line of best of fit with R-2 = 0.778. No such correlation exists between the aromatic Theta(zz) value and the anion binding enthalpy; the line of best fit has R-2 = 0.297. These results are discussed in terms of electrostatic and polarizability contributions to the overall binding enthalpies.