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Electronic ground state of higher acenes
1Chemical Sciences Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. jiangd@ornl.gov
The Journal of Physical Chemistry. A
|December 19, 2007
Summary
Higher acenes exhibit an antiferromagnetic ground state due to zigzag edges, influencing pi-electron localization and spin ordering. This finding clarifies the electronic structure of large polyacenes and related materials.
Area of Science:
- Materials Science
- Quantum Chemistry
- Condensed Matter Physics
Background:
- Acenes are polycyclic aromatic hydrocarbons with potential applications in organic electronics.
- Understanding the electronic ground states of large acenes is crucial for predicting their properties.
- Previous studies have explored smaller acenes, but the behavior of larger systems remains an active research area.
Purpose of the Study:
- To investigate the electronic ground states of acenes with up to 40 fused benzene rings.
- To compare the properties of these acenes with infinite polyacene.
- To elucidate the role of zigzag edges in determining the electronic structure of large acenes.
Main Methods:
- First principles density functional theory calculations were employed.
- Systematic examination of acenes with varying numbers of fused benzene rings.
- Comparison of calculated properties with theoretical models of infinite polyacene.
Main Results:
- Acenes with more than seven fused rings display an antiferromagnetic (open-shell singlet) ground state.
- This singlet state is not necessarily a diradical, with increasing spin separation in larger acenes.
- Zigzag edges are identified as the key structural feature driving pi-electron localization and spin ordering.
Conclusions:
- The electronic ground state of higher acenes and polyacene is governed by zigzag edge effects.
- This provides a consistent explanation for the observed antiferromagnetic behavior in these systems.
- The findings have implications for the design and understanding of organic electronic materials with tailored properties.
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