Mechanical-Bond-Enabled Highly Efficient Charge Separation in a Light-Harvesting Hetero[2]Catenane

Area of Science:

• Materials Science
• Photochemistry
• Supramolecular Chemistry

Background:

• Efficient solar energy conversion relies on effective photodriven charge separation.
• Developing artificial light-harvesting materials with ultrafast charge separation, long-lived states, and minimal energy loss is challenging.

Purpose of the Study:

• To design and synthesize a novel photocatalyst using mechanical bonds for enhanced solar energy conversion.
• To overcome the conventional trade-off between driving force and charge separation efficiency.

Main Methods:

• Employed mechanical bonds to assemble two electron-deficient cationic chromophores (TTzBox⁴⁺ and PDI-C²⁺) into a hetero[2]catenane (TTzPCat⁶⁺).
• Investigated charge separation dynamics and charge-separated state lifetime using spectroscopic techniques.
• Evaluated photocatalytic activity in the selective oxidation of aryl sulfides.

Main Results:

• Achieved ultrafast charge separation (<2.3 ps) with a low driving force (≈160 meV) due to efficient π electronic couplings.
• Prolonged the charge-separated state lifetime (kCS/kCR > 1000) via adaptive molecular conformation and Marcus inverted region effect.
• Demonstrated over a 2-fold enhancement in selective oxidation of aryl sulfides using the TTzPCat⁶⁺ photocatalyst.

Conclusions:

• Mechanical bonding offers a viable strategy for creating advanced photocatalytic materials.
• The developed hetero[2]catenane system surpasses conventional limitations in charge separation efficiency and energy loss.
• This approach provides new insights for designing efficient solar energy conversion systems.