Design of Carbon-Carbon Ylides

Area of Science:

• Organic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Ylides are typically characterized by a carbanionic center adjacent to a positively charged heteroatom.
• Elusive carbon-carbon ylides with zwitterionic sigma bonds have remained a theoretical challenge.
• The norbornane-2,6-dione framework offers a unique scaffold for exploring novel electronic structures.

Purpose of the Study:

• To computationally design and characterize a new class of elusive carbon-carbon ylides.
• To investigate the electronic structure and stability of these zwitterionic species.
• To explore potential applications in materials science, particularly in thermally activated delayed fluorescence (TADF).

Main Methods:

• State-of-the-art computational chemistry methods were employed.
• Density Functional Theory (DFT) was used to analyze electronic structure and stability.
• Time-dependent DFT (TD-DFT) was utilized to assess photophysical properties.

Main Results:

• A new class of carbon-carbon ylides with zwitterionic sigma bonds derived from the norbornane-2,6-dione framework was designed.
• Substitutions on the scaffold stabilize a carbanion at C1 and a carbocation at C7, forming a CC-ylide structure without orbital overlap.
• Large singlet-triplet energy gaps confirm the absence of a diradical ground state, while small T1-S1 gaps suggest TADF potential.
• The cation at C7 was identified as the most reactive site, influencing ylide stability.

Conclusions:

• The designed CC-ylides possess a unique zwitterionic electronic structure.
• These compounds avoid diradical ground states and exhibit properties suitable for TADF materials.
• The identified reactivity site offers insights for future stabilization strategies and functional material design.
• This work opens avenues for exploring novel chemical reactivity and advanced functional materials.