Study of two-centers-one-electron chemical bonds through the quantum interference analysis

• Grant number: 24/18213-5
• Support Opportunities: Scholarships in Brazil - Program to Stimulate Scientific Vocations
• Start date: January 13, 2025
• End date: February 22, 2025
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Marco Antonio Chaer do Nascimento
• Grantee: Alice Barbarino Santos
• Host Institution: Instituto de Química. Universidade Federal do Rio de Janeiro (UFRJ). Ministério da Educação (Brasil)

Abstract

The main objective of this project is to verify the existence of chemical bonds in molecules supposedly containing bonds of the type two-center- 1 electron (2c-1e). These molecules were recently synthesized and the existence of a bond (2c-1e) was proposed based on RX diffraction data. To achieve the proposed objective, we will use the method developed by us, Generalized Product Function-Energy Partitioning (GPF-EP), already well detailed in publications, which is a powerful instrument to characterize the existence or not of a chemical bond between atoms. We have shown in several works that any kind of chemical bond results from quantum interference between mono-electronic states of the atoms involved in the bond. Our method allows to determine the interference energy in each chemical bond of a molecule, separately, as well as the electron density and its components: quasi-classical and interference. It is important to mention that the term "quasi-classical" is being used to designate the portion of both the energy and the electronic density which has classical interpretation (although calculated quantum mechanically), whereas the respective interference components have no classical interpretation, being therefore of purely quantum origin.We start from the proposal of Ruedenberg, that both the total energy and total electronic density can be decomposed in a quasi-classical and an interference portions:E_Total = E_QC+ E_INTand developed general expressions to calculate these quantities from wave functions of the Generalized Valence Bond (GVB) type, which are most appropriate for studying chemical bonding. The resulting expressions form the basis of the Interference Energy Analysis (IEA) method.The (2c-1e) bonds are rarer and more difficult to characterize because they occur, usually, in ionized species. However, Moret and collaborators recently synthesized the molecule tri[2-(di-isopropylphosphine)phenyl]borane-copper(0) (CuTPB). The neutral molecule was characterized by several spectroscopic techniques, including XRD, which revealed a distance between the atoms of Cu and B (2,289 A) smaller than the sum of the atoms' van der Waals radia (3,130 A), which led the authors to propose the existence of a Cu-B bond of type (2c-1e). Using the IEA method, we verified that the quantum interference profile confirmed the existence of the (2c-1e) bond between the Cu and B atoms.More recently, two other molecules were synthesized and again based on interatomic distances obtained by RX diffraction, the authors proposed the existence of a (2c-1e) bond between two tin atoms, in one of the molecules and between two carbon atoms, in the other molecule. These two molecules will be investigated using the EIA method to verify the existence of chemical bonds suggested in the cited works. The dissociation curves will be constructed by scanning along the coordinates Sn-Sn and C-C, at DFT/B3LY level followed by point-to-point (single point) calculations at GVB level, following the same strategy used in the study of the Cu-B connection. (AU)