Simulation of Pump-Push Molecular Dynamics in the Heptazine-H₂O Complex

Area of Science:

• Physical Chemistry
• Chemical Physics
• Spectroscopy

Background:

• Proton-coupled electron transfer (PCET) is crucial in chemical and biological systems.
• Understanding ultrafast charge-separation dynamics is key for designing advanced materials.

Purpose of the Study:

• To investigate electron and proton transfer dynamics in hydrogen-bonded complexes using pump-push-probe spectroscopy.
• To explore the potential of pump-push excitation for controlling PCET reactions on femtosecond timescales.

Main Methods:

• Utilized pump-push-probe spectroscopy to study PCET reactions.
• Employed *ab initio* on-the-fly non-adiabatic trajectory calculations for theoretical analysis.
• Focused on the hydrogen-bonded heptazine-H2O complex.

Main Results:

• A single pump pulse primarily leads to energy relaxation in the heptazine chromophore.
• Re-excitation with a push pulse significantly increases the probability of PCET reactions.
• Demonstrated control over PCET reactivity through tailored excitation pulses.

Conclusions:

• Pump-push excitation is a powerful technique for dissecting and controlling ultrafast PCET processes.
• This approach allows for the study of individual electron and proton transfer events.
• Opens new avenues for manipulating chemical reactions at the femtosecond scale.