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Coupled electron and proton transfer processes in 4-dimethylamino-2-hydroxy-benzaldehyde
Marek Z Zgierski1, Takashige Fujiwara, Edward C Lim
1Steacie Institute for Molecular Science , National Research Council of Canada, Ottawa, K1A 0R6 Canada.
The Journal of Physical Chemistry. A
|August 5, 2011
Summary
This study investigated electron and proton transfer in 4-dimethylamino-2-hydroxy-benzaldehyde (DMAHBA) across different solvents. Solvent polarity significantly influences the excited-state dynamics and charge transfer pathways of DMAHBA.
Area of Science:
- Photochemistry
- Physical Chemistry
- Spectroscopy
Background:
- Understanding excited-state dynamics is crucial for designing new photoactive molecules.
- Solvent effects play a significant role in molecular reaction pathways.
Purpose of the Study:
- To investigate the electron and proton transfer processes in 4-dimethylamino-2-hydroxy-benzaldehyde (DMAHBA).
- To elucidate the influence of solvent polarity on these transfer mechanisms.
Main Methods:
- Time-dependent density functional theory (TDDFT) calculations.
- Picosecond transient absorption (TA) spectroscopy.
- Time-resolved fluorescence studies.
Main Results:
- In nonpolar n-hexane, proton transfer leads to a keto form (ππ* state), with identical TA and fluorescence decay rates.
- In polar acetonitrile, TA shows characteristics of twisted intramolecular charge transfer (TICT) states, distinct from the keto form's fluorescence lifetime.
- Short-lived (∼1 ps) enol form fluorescence observed at ~380 nm (n-hexane) and ~400 nm (acetonitrile).
Conclusions:
- Solvent polarity dictates the dominant excited-state pathways in DMAHBA.
- TDDFT calculations accurately predict the observed proton and electron transfer behaviors in acetonitrile.
- DMAHBA exhibits distinct photochemical behavior in polar versus nonpolar environments.
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