Electronic structure and optical properties of dianionic and dicationic pi-dimers
Yuanzuo Li1, Huixing Li, Xiuming Zhao
1School of Physics and Optoelectronic Technology, and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, People's Republic of China.
The Journal of Physical Chemistry. A
|June 18, 2010
Summary
Theoretical studies reveal two charge-transfer patterns in dianionic/dicationic pi-dimers. These excited states exhibit intermolecular or mixed intra/intermolecular charge transfer, showing electron-hole coherence.
Area of Science:
- Theoretical Chemistry
- Computational Chemistry
- Spectroscopy
Background:
- Dianionic tetrocyanoethylene and dicationic tetrathiafulvalene dimers are systems of interest for understanding electronic interactions.
- Excited state properties and charge transfer mechanisms in molecular dimers are crucial for designing new materials.
Purpose of the Study:
- To theoretically investigate the absorption spectra and excited state nature of dianionic tetrocyanoethylene and dicationic tetrathiafulvalene dimers.
- To elucidate the charge-transfer characteristics and electron-hole dynamics within these pi-dimer systems.
Main Methods:
- Time-dependent density functional theory (TD-DFT) was employed to calculate absorption spectra.
- Coulomb-attenuated model (CAM) was utilized for theoretical analysis.
- Two-dimensional (2D) site and three-dimensional (3D) cube representations (transition density matrix, transition density, charge difference density) were used to visualize excited states.
Main Results:
- Two primary charge-transfer patterns were identified in the excited states: intermolecular charge transfer and a mixture of intramolecular and intermolecular charge transfer.
- The orientation of transition dipole moments was visualized using 3D representations.
- Coupling effects of excitation and electron-hole pair oscillations between monomers were revealed.
- Evidence of electron-hole coherence upon photon excitation was observed.
Conclusions:
- The study provides a detailed theoretical understanding of charge-transfer mechanisms in dianionic/dicationic pi-dimers.
- The findings highlight the importance of considering both intermolecular and intramolecular effects in excited state dynamics.
- The visualization techniques employed offer valuable insights into electron-hole coherence and coupling in molecular systems.
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