Electron transfer and multi-electron accumulation in ExBox⁴⁺

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Materials Science

Background:

• Molecules storing multiple electrons are vital for artificial photosynthesis.
• ExBox(4+) previously accepted electrons via photoexcited guests through space.
• Understanding electron transfer pathways is key for catalyst development.

Purpose of the Study:

• To investigate the through-bond intramolecular electron transfer pathway in ExBox(4+).
• To characterize the electron transfer dynamics and recombination in ExBox(4+).

Main Methods:

• Transient absorption spectroscopy
• Femtosecond stimulated Raman spectroscopy (FSRS)
• X-ray crystallography

Main Results:

• Photoexcitation of ExBox(4+) initiates intramolecular electron transfer from p-xylylene linkers to viologen units.
• Electron transfer occurs in approximately 240 picoseconds.
• Electron recombination occurs in approximately 4 nanoseconds.
• A crystal structure of the doubly reduced ExBox(2+) was obtained.

Conclusions:

• ExBox(4+) exhibits a novel through-bond electron transfer mechanism.
• This pathway is relevant for designing efficient artificial photosynthetic systems.
• The study provides insights into electron storage and transfer in cyclophane molecules.