Non-Statistical Assembly of Donor-Acceptor Cages for Light-Induced Charge Separation.

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Materials Science

Background:

• Donor-acceptor (D/A) assemblies are crucial for charge separation.
• Controlling stoichiometry and stereochemistry in D/A assemblies is challenging.
• Precise positioning of photoredox-active components is key for understanding excited-state dynamics.

Purpose of the Study:

• To develop a method for controlled self-assembly of D/A supramolecular architectures.
• To investigate light-triggered charge separation in these defined architectures.
• To understand the excited-state dynamics and electron transfer pathways.

Main Methods:

• Shape Complementary Assembly (SCA) for exclusive formation of cis-[Pd2D2A2]4+ cages.
• Nuclear Magnetic Resonance (NMR), Mass Spectrometry (MS), and X-ray diffraction for structural analysis.
• Femtosecond pump-probe spectroscopy to study photoexcited state dynamics.

Main Results:

• Exclusive formation of a specific supramolecular cage isomer via SCA.
• Reduced electron transfer pathways compared to statistical assemblies.
• Ultrafast intramolecular charge separation followed by distinct back electron transfer pathways on picosecond and nanosecond timescales.

Conclusions:

• Non-statistical modular self-assembly precisely positions photoredox-active components.
• SCA strategy enables tunable excited-state dynamics in supramolecular architectures.
• This approach offers a platform for designing nanoscale systems for charge separation.