Anharmonic Coupling in a Strong Intramolecular H-Bond System: Contributions to Static and Time-Resolved Vibrational...

Area of Science:

• Chemical Physics
• Molecular Spectroscopy
• Quantum Chemistry

Background:

• Controlling molecular energy flow via vibrational mode-specific manipulation is a significant goal in chemistry.
• Hydrogen-bonded (H-bond) systems offer unique anharmonic coupling channels crucial for energy, proton, and electron transfer processes.

Purpose of the Study:

• To investigate the origin of spectral progressions in the OH stretch (νOH) feature of the mid-infrared absorption spectrum.
• To understand the role of H-bonds in anharmonic coupling and its influence on molecular vibrational modes.

Main Methods:

• Utilized static and time-resolved vibrational spectroscopy.
• Performed anharmonic *ab initio* frequency analysis.
• Focused on the intramolecularly hydrogen-bonded compound 10-hydroxybenzo[h]quinoline (HBQ).

Main Results:

• Identified a distinct finger-like spectral progression within the νOH feature.
• Demonstrated this progression arises from anharmonic coupling between the OH stretch and four low-frequency modes.
• These low-frequency modes are associated with H-bond modulation.

Conclusions:

• Established a model for understanding how low-frequency modes influence OH modes in H-bonded systems.
• Highlighted the importance of H-bond associated anharmonic couplings in molecular dynamics.
• Provided insights into vibrational energy flow control in complex molecular systems.