Photoinduced intra- and intermolecular electron transfer in solutions and in solid organized molecular assemblies

Area of Science:

• Photochemistry
• Molecular Systems
• Electron Transfer

Background:

• Electron transfer (ET) reactions require close proximity of donors and acceptors.
• Achieving efficient ET in solutions is challenging due to concentration and lifetime limitations.
• Covalently linked donor-acceptor (D-A) dyads offer a strategy to overcome these limitations.

Purpose of the Study:

• To systematically study and compare photoinduced electron transfer (ET) in solutions versus molecular systems.
• To investigate the effects of covalently linking donor and acceptor moieties in D-A dyads.
• To explore charge separation and migration dynamics in organized molecular assemblies.

Main Methods:

• Systematic study of photoinduced electron transfer.
• Comparison of ET in solutions and molecular systems (dyads and assemblies).
• Analysis of exciplex formation, charge separation (CS) state lifetimes, and charge migration.

Main Results:

• Covalently linked D-A dyads exhibit accelerated ET rates (>10^12 s^-1) via exciplex intermediates.
• Reduced reorganization energy (0.3 eV) in D-A dyads allows for nanosecond CS state lifetimes.
• Molecular assemblies show complex charge dynamics with intermolecular interactions, leading to microsecond/second lifetimes for interlayer CS states.

Conclusions:

• Covalent linkage and molecular assembly strategies significantly enhance photoinduced electron transfer efficiency and control charge separation.
• The formation of stable charge-separated states with extended lifetimes in organized systems holds promise for future applications.
• Understanding these fundamental photochemistry aspects is crucial for designing advanced molecular materials.