Internal Rotation of Disilane and Related Molecules:a Density Functional Study

TL;DR

This study uses density functional theory to analyze the internal rotation barriers and electronic properties of disilane and related molecules, revealing stable conformations and electronic density changes during torsion.

Contribution

It provides detailed DFT calculations on Si_2H_6, Si_2F_6, Si_2Cl_6, and Si_2Br_6, highlighting their conformational preferences and electronic behavior during rotation.

Findings

Molecules favor staggered conformations with energy barriers.

Chemical potential and hardness vary among molecules during rotation.

Torsional motion affects nucleophilic attack mechanisms.

Abstract

DFT calculations performed on Si_2H_6, Si_2F_6, Si_2Cl_6, and Si_2Br_6 are reported. The evolution of the energy, the chemical potential and the molecular hardness, as a function of torsion angle, is studied. Results at the DFT-B3LYP/6-311++G** level show that the molecules always favor the stable staggered conformations, with low but significant energy barriers that hinder internal rotation. The chemical potential and hardness of Si_2H_6 remains quite constant as the sylil groups rotate around the Si-Si axis, whereas the other systems exhibit different degrees of rearrangement of the electronic density as a function of the torsion angle. A qualitative analysis of the frontier orbitals shows that the effect of torsional motion on electrophilic attack is negligible, whereas this internal rotation may generate different specific mechanisms for nucleophilic attack.