Nature of the Chemical Bond and Origin of the Inverted Dipole Moment in Boron Fluoride: A Generalized Valence Bond Approach
Nature of the Chemical Bond and Origin of the Inverted Dipole Moment in Boron Fluoride: A Generalized Valence Bond Approach
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DOI：
10.1021/jp510085r
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发表时间：
2015-05-28
影响因子：
2.9
通讯作者：
Chaer Nascimento, Marco Antonio
中科院分区：
文献类型：
--
作者：
Fantuzzi, Felipe;Cardozo, Thiago Messias;Chaer Nascimento, Marco Antonio
用广义乘积函数能量分配(GPF-EP)方法研究了BF分子中化学键的性质和倒偶极矩的来源。计算采用GPF波函数，将所有核心电子视为一个Hartree-Fock基团，价电子处于广义价键完全配对(GVB-PP)或全GVB水平，基组为cc-pVTZ。结果表明，X(1)Sigma(+)和a(3)PI态的化学结构都是由单键组成的。激发态较低的解离能归因于键解离后稳定的B2SP类叶轨道的原子内单重态耦合。BF基态电偶极反转的主要原因是类硼2SP叶轨道的重新取向导致B原子上电子密度的增加。结果表明，在这两种状态下，pi从氟到硼的反向键合对电子密度向键区的移动起着次要的作用。此外，这种效应只与电子密度的准经典分量的变化有关，而不会导致这两种态的共价性。因此，至少对于BF分子的情况，术语背键合是误导的，因为它不有助于键的形成。
The generalized product function energy partitioning (GPF-EP) method has been applied to investigate the nature of the chemical bond and the origin of the inverted dipole moment of the BF molecule. The calculations were carried out with GPF wave functions treating all of the core electrons as a single Hartree-Fock group and the valence electrons at the generalized valence bond perfect-pairing (GVB-PP) or full GVB levels, with the cc-pVTZ basis set. The results show that the chemical structure of both X (1)Sigma(+) and a (3)Pi states is composed of a single bond. The lower dissociation energy of the excited state is attributed to a stabilizing intraatomic singlet coupling involving the B 2sp-like lobe orbitals after bond dissociation. An increase of electron density on the B atom caused by the reorientation of the boron 2sp-like lobe orbitals is identified as the main responsible effect for the electric dipole inversion in the ground state of BF. Finally, it is shown that pi back-bonding from fluorine to boron plays a minor role in the electron density displacement to the bonding region in both states. Moreover, this effect is associated with changes in the quasi-classical component of the electron density only and does not contribute to covalency in either of the states. Therefore, at least for the case of the BF molecule, the term back-bonding is misleading, since it does not contribute to the bond formation.