Organohelium compounds: structures, stabilities and chemical bonding analyses

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Organic Chemistry

Background:

• Investigating novel bonding interactions is crucial for expanding chemical understanding.
• Helium's inert nature typically precludes strong bonds with organic molecules.
• Exploring the potential for unusual chemical bonds can lead to new molecular structures.

Purpose of the Study:

• To investigate the feasibility of forming carbon-helium (C-He) bonds in organic molecules.
• To characterize the structural, energetic, and topological properties of He(+)-substituted organic cations.
• To determine the stability and bonding nature of these novel C-He interactions.

Main Methods:

• High-level computational calculations were employed for structural and energetic analysis.
• Topological characterization using Atoms in Molecules (AIM) and Electron Localization Function (ELF) methods.
• Analysis of stability with respect to neutral helium release and C-C bond cleavage.

Main Results:

• Stable C-He bonds can form in organic molecules upon substitution of approximately half the hydrogen atoms with He(+).
• Calculated C-He bond distances range from 1.129 Å to 1.327 Å.
• He(+) substitution can lead to weak charge-shift interactions, with He2CO(2+) showing a non-negligible covalent contribution.

Conclusions:

• The formation of C-He bonds is possible, leading to a potentially unlimited number of new, stable chemical species.
• Most He(+)-substituted hydrocarbons are metastable, except for ethene derivatives.
• Topological analysis reveals the nature of the C-He bond and electronic structure modifications, with He2CO(2+) being a unique case.