Instituto de Química, Universidade Estadual de Campinas, Campinas, SP, Brazil.
J Phys Chem A. 2011 Nov 17;115(45):12572-81. doi: 10.1021/jp202929s. Epub 2011 Jul 6.
Infrared fundamental vibrational intensities and quantum theory atoms in molecules (QTAIM) charge-charge flux-dipole flux (CCFDF) contributions to the polar tensors of the fluorochloromethanes have been calculated at the QCISD/cc-pVTZ level. A root-mean-square error of 20.0 km mol(-1) has been found compared to an experimental error estimate of 14.4 and 21.1 km mol(-1) for MP2/6-311++G(3d,3p) results. The errors in the QCISD polar tensor elements and mean dipole moment derivatives are 0.059 e when compared with the experimental values. Both theoretical levels provide results showing that the dynamical charge and dipole fluxes provide significant contributions to the mean dipole moment derivatives and tend to be of opposite signs canceling one another. Although the experimental mean dipole moment derivative values suggest that all the fluorochloromethane molecules have electronic structures consistent with a simple electronegativity model with transferable atomic charges for their terminal atoms, the QTAIM/CCFDF models confirm this only for the fluoromethanes. Whereas the fluorine atom does not suffer a saturation effect in its capacity to drain electronic charge from carbon atoms that are attached to other fluorine and chlorine atoms, the zero flux electronic charge of the chlorine atom depends on the number and kind of the other substituent atoms. Both the QTAIM carbon charges (r = 0.990) and mean dipole moment derivatives (r = 0.996) are found to obey Siegbahn's potential model for carbon 1s electron ionization energies at the QCISD/cc-pVTZ level. The latter is a consequence of the carbon mean derivatives obeying the electronegativity model and not necessarily to their similarities with atomic charges. Atomic dipole contributions to the neighboring atom electrostatic potentials of the fluorochloromethanes are found to be of comparable size to the atomic charge contributions and increase the accuracy of Siegbahn's model for the QTAIM charge model results. Substitution effects of the hydrogen, fluorine, and chlorine atoms on the charge and dipole flux QTAIM contributions are found to be additive for the mean dipole derivatives of the fluorochloromethanes.
在 QCISD/cc-pVTZ 水平上，计算了氟氯甲烷的红外基本振动强度和量子理论原子在分子（QTAIM）电荷-电荷通量-偶极通量（CCFDF）对极性张量的贡献。与 MP2/6-311++G(3d,3p)结果的实验误差估计值 14.4 和 21.1 km mol(-1)相比，发现均方根误差为 20.0 km mol(-1)。与实验值相比，QCISD 偶极矩导数的极性张量元素误差为 0.059 e。这两个理论水平都提供了结果，表明动力学电荷和偶极通量对平均偶极矩导数有显著贡献，并且趋于相互抵消。尽管实验平均偶极矩导数值表明所有氟氯甲烷分子的电子结构都符合简单的电负性模型，其末端原子具有可转移的原子电荷，但 QTAIM/CCFDF 模型仅确认氟甲烷具有这种结构。虽然氟原子在从与其相连的其他氟原子和氯原子上吸取电子电荷的能力上没有饱和效应，但氯原子的零通量电子电荷取决于其他取代原子的数量和种类。QTAIM 碳电荷（r = 0.990）和平均偶极矩导数（r = 0.996）都符合 Siegbahn 的碳 1s 电子电离能 QCISD/cc-pVTZ 水平的势能模型。这是由于碳平均导数遵循电负性模型，而不一定与其与原子电荷的相似性有关。氟氯甲烷中原子偶极对相邻原子静电势的贡献与原子电荷贡献相当大，提高了 QTAIM 电荷模型结果的 Siegbahn 模型的准确性。氢、氟和氯原子对氟氯甲烷的电荷和偶极通量 QTAIM 贡献的取代效应被发现是可加的，对于氟氯甲烷的平均偶极导数。
