Understanding and Controlling Short- and Long-Range Electron/Charge-Transfer Processes in Electron Donor-Acceptor...

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Materials Science

Background:

• Development of artificial photosynthetic systems requires efficient charge separation and transfer.
• Multicomponent conjugates offer tunable platforms for controlling electron dynamics.
• Understanding charge recombination pathways is crucial for designing stable charge-separated states.

Purpose of the Study:

• To synthesize and characterize novel multicomponent electron donor-donor-acceptor conjugates.
• To investigate the influence of molecular bridges on charge separation and recombination dynamics.
• To elucidate the mechanisms governing the formation of long-lived charge-separated states.

Main Methods:

• Experimental synthesis and characterization of zinc-porphyrin (ZnP), ferrocene (Fc), and C60-fullerene conjugates.
• Femto-, pico-, nano-, and microsecond transient absorption spectroscopy.
• Computational modeling and multiwavelength/target analyses.

Main Results:

• Demonstrated control over electron and hole shuttling using tunable p-phenylene-acetylene/acetylene bridges.
• Confirmed the formation of two adjacent charge-transfer states (C60-ZnP•−-Fc•+ and C60•−-ZnP•+-Fc) en route to a distant C60•−-ZnP-Fc•+ state.
• Established the critical role of molecular bridge properties (reorganization energy, damping factor) and solvent polarity in dictating charge-transfer outcomes and rate constants.

Conclusions:

• The molecular wire-like nature of bridges is decisive for generating distant and long-lived charge-separated states.
• Charge recombination occurs in different Marcus parabola regions (inverted for adjacent, normal for distant states).
• Tuning bridge properties and solvent polarity allows for optimization of charge-transfer processes in artificial systems.