Electronic Force Density Fields: Insights into Partial Bonds, Transition States, and Chemical Structure Evolution.

Area of Science:

• Quantum Chemistry
• Chemical Physics
• Theoretical Chemistry

Background:

• Understanding chemical bonds, especially partial bonds in transition states, is crucial for reaction mechanisms.
• Existing models struggle to fully explain the complex interactions within semibroken and semiformed partial chemical bonds.

Purpose of the Study:

• To introduce and validate the quantum-topological binding approach for analyzing partial chemical bonds.
• To elucidate the nature of interatomic interactions and chemical structure in transition states.
• To draw parallels between partial bonds and noncovalent interactions.

Main Methods:

• Simultaneous analysis of electrostatic force density, total static force density, and electron density gradient fields.
• Identification of zero-flux boundaries to define interatomic charge transfer (ICT) and quantum chemical response (QCR).
• Examination of atomic and pseudoatomic charge changes during substitution reactions.

Main Results:

• The quantum-topological binding approach reveals discrepancies attributed to nonclassical electron-electron interactions.
• Interatomic charge transfer (ICT) and electron-transfer-induced quantum chemical response (QCR) phenomena were identified.
• Parallels were drawn between partial bonds and noncovalent interactions, both showing incomplete QCRs and partial electron sharing.
• Polarization effects due to electronegativity differences during bond breaking were observed.

Conclusions:

• The quantum-topological binding approach provides a robust framework for understanding partial chemical bonds.
• Partial bonds exhibit characteristics similar to noncovalent interactions, involving incomplete electron sharing.
• The study offers insights into chemical structure evolution and bond delocalization mechanisms.