NHC-Terphenyl Radicals and Anions: Tuning Stability and Redox Properties via Substituent Patterning

Area of Science:

• Organometallic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• N-heterocyclic carbenes (NHCs) are versatile ligands in organometallic chemistry.
• The electronic and steric properties of NHCs can be tuned by substituents.
• Terphenyl groups are often used to modify the properties of organic molecules.

Purpose of the Study:

• To investigate the influence of para-terphenyl versus meta-terphenyl substitution on NHC redox behavior.
• To evaluate the stability of radicals and anions derived from these functionalized NHCs.
• To understand how structural modifications affect the electronic properties of NHC complexes.

Main Methods:

• Synthesis of NHC-terphenyl complexes via nickel catalysis.
• Electrochemical characterization using cyclic voltammetry (CV).
• Chemical reduction using KC8 to generate radical anions and computational studies.

Main Results:

• Para-terphenyl substituted NHC cations showed two reversible redox events.
• Meta-terphenyl substituted NHC cations exhibited less reversible redox behavior.
• Stable radicals and anions were generated, with para-terphenyl derivatives showing greater stability.
• Structural and computational analyses supported the experimental observations.

Conclusions:

• The terphenyl substitution pattern critically influences the redox properties and stability of NHC-derived radicals and anions.
• Para-terphenyl substitution generally leads to more stable radical and anionic species compared to meta-terphenyl.
• This study provides insights into the rational design of NHC-based functional materials.