Estudo computacional de ligações químicas tetrel em tetrafluoretos

Abstract

The study of chemical bonds has been of interest to many scientists even before the creation of quantum mechanics. In recent years, several theories have been established in quantum mechanics that sought to describe the type of interaction present in the chemical bond. Traditionally, the bonds between atoms are one of the bases of Chemistry, being able to explain and understand the main properties of substances. Among the different types of chemical bonds that are reported in the literature, it can be observed that hydrogen bonds are extensively investigated, being of fundamental importance for the explanation of several chemical and biochemical processes. In addition to this, there is a significant type of interaction, called non-covalent, that has attracted the attention of many researchers due to its extensive applications in chemistry, physics, biology and related fields. Such an interaction is called tetrel bond, which was defined as an interaction between an element of Group 14, acting as a Lewis acid center and a Lewis base, which can interact by isolated electron pairs. This research aimed to apply the OP model, which is a method of analyzing chemical bonds based on the overlap properties, to analyze the interactions of tetrafluorides with NH3, PH3 and AsH3 ligands. The objective was also to compare the results of the overlap model with the results obtained with the QTAIM model. In this sense, the geometries of the analyzed complexes were optimize at the ωB97X-D level with the aug-cc-pVDZ base set using the GAMESS program. The localized molecular orbitals were used in the scope of the overlap model, where they were obtained using the Pipek-Mezei method. Overlap properties were calculated using ChemBOS software, while properties of the QTAIM model were obtained using MULTIWFN software. The results indicate that Lewis acid centers interacting with only one base always adopt a tetrahedral or bipiramidal geometry with a distorted triangular base. On the other hand, the interaction with two bases induced the Lewis acid flatness. For the overlap model, the lower values of αOP indicated a lesser polarizable bond overlap. The values J_OP^intra and ρOP, on the other hand, indicate an intense change in the sharing of density and compactness of the overlap. Regarding the results of the QTAIM model, the complexes with values of ∇2ρ(r)>0 in a BCP, indicate that the density concentrations are more located close to the atomic nuclei (closed layer interaction, characterizing a less covalent bond) and when the values of ∇2ρ(r)<0, indicate that the highest density concentrations in the regions close to the BCP (shared interaction, that is, covalent bonding). In view of the above, the results of the properties of the overlap model and the QTAIM model in most of the analyzes are convergent. It is notorious that the results of both models indicate that most of the interactions analyzed have a less covalent character. Therefore, the interpretation of both results, in part, addresses a compatibility of information that helps in understanding about Lewis acid and base interactions.