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A Macrocyclic Furan with Accessible Oxidation States: Switching Between Aromatic and Antiaromatic Global Ring
Or Dishi1, Yuval Rahav1, Raanan Carmieli2
1Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|August 6, 2022
Summary
Macrocyclic furans can now switch aromaticity due to accessible oxidation states. Methylene-substituted macrocycles achieve a 30π electron aromatic state, showing potential as p-type materials.
Area of Science:
- Organic Chemistry
- Materials Science
- Theoretical Chemistry
Background:
- Macrocyclic furans are theoretically capable of switching aromaticity based on oxidation state.
- Existing macrocyclic furans are stabilized by electron-withdrawing groups, hindering accessible oxidation states.
Purpose of the Study:
- To synthesize macrocyclic furans with accessible oxidation states.
- To investigate the aromaticity switching behavior of these new compounds.
- To explore their potential as p-type materials.
Main Methods:
- Post-macrocyclization synthesis of methylene-substituted macrocyclic furans.
- Electrochemical analysis to determine oxidation potential.
- Nuclear Magnetic Resonance (NMR) spectroscopy to observe diatropic currents.
- Nuclear Independent Chemical Shift (NICS) and Aromaticity in Conjugated Systems (ACID) calculations.
Main Results:
- Methylene-substituted macrocyclic furans exhibit a low oxidation potential (-0.23 vs. Fc/Fc+).
- Partial oxidation occurs under ambient conditions.
- Further oxidation to the dication induces aromaticity switching to a 30π electron aromatic state.
- Strong diatropic currents and distinct current pathways were observed in NMR, NICS, and ACID calculations for neutral and dicationic states.
Conclusions:
- Macrocyclic furans can be engineered to possess stable and accessible oxidation states.
- Aromaticity switching is achievable in these systems.
- Methylene-substituted macrocyclic furans show promise as p-type organic materials.
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