Visible Light-Driven Artificial Molecular Switch Actuated by Radical-Radical and Donor-Acceptor Interactions

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Materials Science

Background:

• Mechanical interlocking of molecular components offers unique functionalities.
• Photosensitizers can drive redox reactions for molecular control.
• Donor-acceptor interactions are crucial for molecular recognition and assembly.

Purpose of the Study:

• To design and synthesize a visible light-driven switchable [2]catenane.
• To demonstrate photochemical and chemical control over the molecular switch.
• To investigate the redox-driven movement of the catenane components.

Main Methods:

• Synthesis of a [2]catenane comprising Ru(bpy)3(2+)-tethered cyclobis(paraquat-p-phenylene) (CBPQT(4+)) and a macrocyclic polyether.
• Utilizing visible light irradiation and triethanolamine (TEOA) for reduction.
• Employing oxygen for oxidation to revert the system.

Main Results:

• The CBPQT(4+) ring selectively encircles the electron-rich 1,5-dioxynaphthalene (DNP) site in the oxidized state.
• Visible light-driven reduction by TEOA causes the CBPQT(2(•+)) ring to move to the electron-deficient 4,4'-bipyridinium (BIPY(2+)) site, forming a trisradical complex.
• Oxidation by O2 in the dark restores the original configuration, encircling the DNP site.

Conclusions:

• A prototypical molecular switch based on a visible light-driven [2]catenane has been successfully demonstrated.
• The switch exhibits reversible manipulation through sequential photochemical reduction and chemical oxidation.
• This work highlights the potential of redox-controlled mechanical movement in supramolecular systems.