Highly Stable Organic Bisradicals Protected by Mechanical Bonds

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Catenanes are mechanically interlocked molecular architectures.
• Persistent organic radicals are valuable for materials science but often lack stability.
• Radical host-guest templation is a method for synthesizing radical species.

Purpose of the Study:

• To synthesize novel, highly charged [2]catenanes.
• To investigate the stability and properties of these new catenanes.
• To explore their potential applications in advanced materials.

Main Methods:

• Synthesis via radical host-guest templation using BIPY radical cations and cyclobis(paraquat-p-phenylene).
• Characterization using X-ray crystallography and Electron Paramagnetic Resonance (EPR) spectroscopy.
• Electrochemical studies to determine redox properties.

Main Results:

• Successful synthesis of two new highly charged [2]catenanes, which exist as air-stable singlet bisradicals.
• X-ray crystallography and EPR confirmed the bisradical nature and stability.
• Electrochemical analysis revealed significantly positive reduction potentials, contributing to air stability.
• Unique Near-Infrared (NIR) absorption properties were observed for mono- and bisradical states.

Conclusions:

• The synthesized [2]catenanes are exceptionally stable singlet bisradicals.
• Mechanical-bond-induced stabilization is an effective strategy for designing persistent organic radicals.
• These catenanes show promise for applications in NIR photothermal conversion, electrochromic devices, and memory devices.