Topological classification of cycloadditions occurring on-surface and in the solid-state.

Area of Science:

• Organic Chemistry
• Materials Science
• Computational Chemistry

Background:

• Cycloaddition mechanisms are key to synthesizing sp2 carbon nanostructures like graphene.
• Current reaction modeling often overlooks symmetry effects, focusing only on exothermic products.

Purpose of the Study:

• To introduce a method for classifying symmetry-forbidden reaction pathways using topological tools.
• To explore the role of topological classification in understanding cycloaddition mechanisms for nanographene engineering.

Main Methods:

• Development of a scheme for classifying symmetry-forbidden reaction coordinates in Woodward-Hoffmann diagrams.
• Application of topological classifiers to analyze polycyclic aromatic azomethine ylide (PAMY) cycloadditions.
• Utilizing tight-binding reaction models and broken-symmetry density functional theory (DFT).

Main Results:

• Topological classifiers provide a unified approach to studying reaction pathways and correlation diagrams.
• Identified topologically-allowed pathways for an endothermic reaction mechanism in PAMY cycloadditions.
• Demonstrated that exothermic pathways can be topologically forbidden.

Conclusions:

• Topological classification is essential for accurate reaction modeling in nanographene engineering.
• This approach is fundamental for designing on-surface and solid-state cycloaddition reactions.
• Highlights the importance of considering symmetry and topology beyond simple energetics.