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Metaphenylene-based nitroxide diradicals: a protocol to calculate intermolecular coupling constant in a
Tumpa Sadhukhan1, Shekhar Hansda, Iqbal A Latif
1Department of Chemistry, Indian Institute of Technology-Bombay Powai , Mumbai 400 076, India.
The Journal of Physical Chemistry. A
|November 26, 2013
Summary
This study determines magnetic exchange coupling constants in diradicals using density functional theory. The M06-2X functional offers the most accurate predictions for these important molecular interactions.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Molecular Magnetism
Background:
- Metaphenylene-based dinitroxide diradicals are key systems for studying magnetic exchange coupling.
- Accurate determination of intramolecular magnetic exchange coupling constants (J) is crucial for understanding molecular magnetism.
Purpose of the Study:
- To evaluate the performance of various unrestricted density functional theory (UDFT) hybrid functionals for calculating magnetic exchange coupling constants in diradicals.
- To develop a method for determining both intramolecular (J) and intermolecular (J') coupling constants from quantum chemical calculations.
Main Methods:
- Unrestricted Density Functional Methodology (UDFT) with hybrid functionals (B3LYP, B3LYP-D3, M06-2X, HSE, LC-ωPBE).
- Geometry optimizations using the 6-311G(d,p) basis set for triplet and broken symmetry states.
- Application of UDFT to N-mers (N=2-6) of diradicals to determine intermolecular coupling constants.
Main Results:
- M06-2X functional provided the most realistic magnetic exchange coupling constants, while B3LYP overestimated them.
- HSE and LC-ωPBE functionals showed significant deviations from experimental values.
- The study successfully derived expressions and computational methods to determine both intramolecular and intermolecular coupling constants, showing good agreement with experimental data.
Conclusions:
- The M06-2X functional is recommended for accurate calculations of magnetic exchange coupling in these diradical systems.
- The developed method provides a reliable approach for quantifying intramolecular and intermolecular magnetic interactions in extended systems.
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