Bis-[cyclic(alkyl)(amino)carbene]-derived diradicals

Area of Science:

• Organometallic Chemistry
• Polymer Science
• Organic Synthesis

Background:

• Carbene ligands are crucial in catalysis and materials science.
• Polymeric structures offer unique properties for advanced applications.
• Diradicals are reactive intermediates with potential in various chemical transformations.

Purpose of the Study:

• To synthesize and characterize crystalline polymeric structures of N-tethered bis-CAACs.
• To utilize these polymers as building blocks for novel diradical compounds.
• To investigate the electronic and magnetic properties of the resulting diradicals.

Main Methods:

• Synthesis of crystalline LiOTf adducts of trans-1,4-cyclohexylene bridged N-tethered bis-CAACs.
• Utilizing these adducts as precursors for diradical synthesis.
• Electron Paramagnetic Resonance (EPR) spectroscopy for diradical character confirmation.
• Theoretical calculations (e.g., DFT) to determine electronic state stability.

Main Results:

• Successful synthesis and isolation of crystalline polymeric bis-CAAC LiOTf adducts.
• Formation of crystalline (amino)(carboxy)-based diradicals from these polymeric precursors.
• Unambiguous confirmation of triplet diradical character via EPR spectroscopy (half-field signal).
• Theoretical calculations indicate a marginal preference for the singlet state over the triplet state.

Conclusions:

• Crystalline polymeric bis-CAACs serve as effective building blocks for diradical synthesis.
• The synthesized diradicals exhibit significant triplet diradical character.
• The interplay between singlet and triplet states in these diradicals warrants further investigation.