Exploiting the (-C-H···C-) Interaction to Design Cage-Functionalized Organic Superbases and Hyperbases: A...

Area of Science:

• Computational Chemistry
• Organic Chemistry
• Supramolecular Chemistry

Background:

• P-ylide compounds are known for their unique chemical properties.
• Pentacyclo[5.4.0.02,6.03,10.05,9]undecane (PCU) and pentacyclo [6.4.0.02,7.03,11.06,10] dodecane (PCD) scaffolds offer rigid, complex frameworks.

Purpose of the Study:

• To computationally investigate carbon center-based P-ylide substituting bases.
• To evaluate the basicity and interaction mechanisms of P-ylides on PCU and PCD scaffolds.

Main Methods:

• Density Functional Theory (DFT) calculations using B3LYP-D3/6-311+G(d,p) level of theory.
• Analysis of proton affinities, Atoms in Molecules (AIM), and Natural Bond Orbital (NBO) calculations.
• Investigation of isodesmic reactions to understand energetic contributions.

Main Results:

• Calculated proton affinities indicate superbase and hyperbase characteristics.
• Intramolecular -C-H···C- interactions significantly enhance basicity.
• Low free activation energy for proton exchange observed in substituted PCD and PCU systems.
• -C-H···C- interactions were compared to conventional -N-H···N- hydrogen bonds.

Conclusions:

• The studied P-ylide systems represent potent superbases.
• Basicity is tunable via modification of intramolecular -C-H···C- interactions.
• Superbasicity arises from a combination of ring strain, steric repulsion, and favorable intramolecular interactions.