Computation of quantum mechanical hybridization and dipole correlation of the electronic structure of the F₃B–NH₃supermolecule

Abstract

ABSTRACT:A valence bond description of the electronic structure and the process of the formation of the adduct supermolecule, F 3 B-NH 3 by charge transfer interactions between a Lewis acid, BF 3 , and a Lewis base, NH 3 , is computed in terms of the quantum mechanical localized molecular orbital (LMO) method. A dipole correlation of electronic structure is also reported. The valence bond description in terms of bond pair and lone pair is transparent in the generated LMOs of the donor, acceptor, and adduct supermolecule. It is transparent in the computed LMOs that the lone pair of N in NH 3 is actually involved in forming a new dative bond between B and N atoms. The present work reports the evaluated hybridization status of the boron, nitrogen, and fluorine atoms in the interesting donor-acceptor compound, F 3 B-NH 3 . It is transparent in the computed results that the quantum mechanical hybridization automatically incorporates the effect of change of environment in the pattern of hybridization perfectly in accordance with Bent's rule. The calculated dipole moment of the supermolecule is high; it is partitioned into contributions resulting from bond moments and atomic dipoles, as contributions from hybrid orbitals accommodating lone pairs of electrons. The magnitude of atomic dipole is small compared with the bond dipole component. A rationale of the bond moment of the molecule is attempted in terms of the charge density distribution on atomic sites and the atomic dipole is correlated in terms of the pattern of hybridization of lone pairs on the F atoms. The generated LMOs reveal that only one lone pair on each F atom is in a hybrid orbital, and the remaining two lone pairs are in pure p orbitals. The small lone pair contribution to molecular dipole is thus transparent in computed quantum mechanical hybridization that shows that, out of three, only one lone pair on the F atoms can set in atomic dipole. This study demonstrates that atomic dipole can be used as a descriptor of the hybridization status of lone pairs on atoms in the molecules.

Dipole Correlation of the Electronic Structures of theConformations of Water Molecule Evolving Through theNormal Modes of Vibrations Between Angular (C2v) to Linear(D∝h) Shapes

“…The hybridization status of lone pair is straightforward in quantum mechanical localized molecular orbitals and the dipole partitioning can ascertain the contribution of lone pairs into molecular dipoles. The lone pair component of molecular dipole and the hybridization status of lone pair are complementary to each other [22]. Thus we can argue that the dipole moment can be used as descriptor of charge density distribution and the hybridization status in lone pairs of electrons in molecules.…”

“…We [22,[36][37][38] have found that the hybridizations of lone pairs and bond pairs are straightforward in the LMO's generated from CMO's by unitary transformation. We have also tested the efficiency of the method of localization suggested by Sinanoğlu [39,40] that the method is fast, efficient and requires less computer time.…”

“…In the above premise, it may be argued that the bond moments are usually small and can be offset by symmetry of the shapes of the molecules. Thus it may be argued that molecules with lone pairs of electrons should have high dipole moments [20,21,22] and the total dipole of hetero-atomic molecules with lone pairs should have two components -bond moment and lone pair moment-…”

“…It, therefore, transpires that the lone pair(s) of O atom has a definite contribution to the dipole moment of water molecule. We [22] have recently found that dipole moment can be a descriptor of electronic structure of molecules containing lone pair electrons. The hybridization status of lone pair is straightforward in quantum mechanical localized molecular orbitals and the dipole partitioning can ascertain the contribution of lone pairs into molecular dipoles.…”

“…We, therefore, bring the suggestion that [12,18] one lone pair resides in pure p-type and the other lone pair resides in pure s type orbital of O atom and also the qualitative "Squirrel Ears" structure of water molecule under serious scrutiny. To settle the problem whether the lone pairs of electrons on the oxygen atom of water molecule are accommodated in a pure or a hybrid orbital, we propose to exploit conveniently the method of dipole correlation of electronic structure recently suggested by us [22]. We want to proceed a bit more.…”