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Published on: October 30, 2012
Time-Resolved Photoelectron Spectroscopy of 1,3-Dimethyluracil and 1,3-Dimethylthymine
Wenping Wu1,2, Yuhuan Tian1,2, Baihui Feng1,3
1State Key Laboratory of Chemical Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning116023, China.
The Journal of Physical Chemistry. A
|July 27, 2026
Summary
Ultrafast electronic relaxation dynamics in 1,3-dimethyluracil and 1,3-dimethylthymine were studied. Methylation at the 5-position influences the population and decay of excited states, with 1,3-dimethylthymine showing a higher yield of the S1 state.
Area of Science:
- Photochemistry
- Physical Chemistry
- Molecular Spectroscopy
Background:
- Understanding excited-state dynamics is crucial for photochemistry.
- Pyrimidine derivatives like uracil and thymine are biologically significant.
- Methylation can alter molecular electronic properties and reactivity.
Purpose of the Study:
- To investigate the ultraviolet-induced electronic relaxation pathways of 1,3-dimethyluracil and 1,3-dimethylthymine.
- To elucidate the role of 5-position methylation in excited-state dynamics.
- To compare the population and decay kinetics of excited states between the two molecules.
Main Methods:
- Femtosecond time-resolved photoelectron spectroscopy (fs-TRPES) was employed.
- Analysis of fs-TRPES spectra to determine time constants and spectral features.
- Comparison of decay-associated spectra for mechanistic insights.
Main Results:
- An ultrashort decay time constant (<100 fs) was observed for the initially populated S2(1ππ*) state in both molecules.
- Subsequent population of the dark S1(1nπ*) state was detected, followed by decay within picoseconds.
- Differences in excited-state dynamics suggest varying quantum yields for the S1 state between 1,3-dimethyluracil and 1,3-dimethylthymine.
Conclusions:
- The study reveals distinct ultrafast electronic relaxation dynamics for 1,3-dimethyluracil and 1,3-dimethylthymine.
- Methylation at the 5-position appears to influence the quantum yield of the S1(1nπ*) state, potentially favoring 1,3-dimethylthymine.
- fs-TRPES is a powerful technique for probing excited-state dynamics in substituted nucleobases.
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