Ultrafast Electron Transfer in a Self-Assembling Sulfonated Aluminum Corrole-Methylviologen Complex

Area of Science:

• Photochemistry
• Materials Science
• Spectroscopy

Background:

• Mimicking natural photosynthesis is key for solar energy.
• Corroles are promising donor materials for artificial photosynthesis.
• Donor-acceptor complexes are essential for charge separation.

Purpose of the Study:

• To comprehensively study ultrafast photoinduced electron transfer in a self-assembling sulfonated aluminum corrole-methylviologen complex.
• To investigate the dynamics of charge separation and back electron transfer using advanced spectroscopy.
• To understand energy relaxation and electronic reorganization after photoexcitation.

Main Methods:

• Visible and mid-infrared transient absorption spectroscopy.
• Ultrafast spectroscopy to probe electron transfer dynamics on femtosecond to picosecond timescales.
• Analysis of specific vibrational modes (methylviologen-radical and corrole C=C) to track energy transfer.

Main Results:

• Observed initial forward electron transfer from corrole to methylviologen on a ~130 fs timescale.
• Measured back electron transfer with a rate of τ_BET = (1.8 ± 0.5) ps.
• Identified significant excess energy surviving back transfer, leading to hot ground state absorption and a 10-15% charge-separation yield after 300 ps.

Conclusions:

• The corrole-methylviologen complex exhibits complex ultrafast electron transfer dynamics.
• Mid-IR spectroscopy is crucial for unraveling back electron transfer and cooling dynamics.
• The system demonstrates potential for solar energy applications, despite a high back electron transfer rate.