σ-Holes and Si···N intramolecular interactions.

Area of Science:

• Computational chemistry
• Inorganic chemistry
• Molecular modeling

Background:

• Investigating noncovalent interactions is crucial for understanding molecular behavior.
• Short silicon-nitrogen (Si···N) distances in certain molecules suggest potential interactions.
• The nature of these Si···N interactions requires detailed computational analysis.

Purpose of the Study:

• To computationally investigate the presence and nature of Si···N interactions.
• To explore the influence of molecular structure and substituents on Si···N interactions.
• To determine the driving forces behind the observed Si···N distances.

Main Methods:

• Density functional theory (DFT) calculations using the M06-2X/6-31+G(d,p) level of theory.
• Optimization of molecular geometries to find stable conformations.
• Calculation of energies and electrostatic potentials to analyze interactions.

Main Results:

• Confirmed an attractive Coulombic Si···N interaction in both Si-O-N and Si-(CH2)n-N systems.
• Identified the interaction involving nitrogen lone pairs and silicon σ-holes, influenced by anti substituents.
• Observed that Si···N distances are dependent on the electron-withdrawing nature of substituents and molecular conformation.

Conclusions:

• The study confirms the presence of a weak but significant attractive Coulombic Si···N interaction.
• The interaction strength is modulated by the electronic properties of silicon substituents and molecular geometry.
• These findings provide insights into the bonding and structural characteristics of silicon-nitrogen compounds.