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Published on: September 26, 2016
(19)F spin-spin coupling in peri-difluoronaphthalene.
1Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01224, Warsaw, Poland. michaljz@icho.edu.pl
Physical Chemistry Chemical Physics : PCCP
|May 22, 2009
Summary
We calculated nuclear magnetic resonance (NMR) spin-spin coupling tensors for fluorine-19 in peri-difluoronaphthalene. Our quantum chemical results confirm experimental findings on the significant anisotropic contribution to the four-bond fluorine-fluorine coupling.
Area of Science:
- Quantum Chemistry
- Computational Spectroscopy
- Magnetic Resonance
Background:
- Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool for elucidating molecular structure.
- Spin-spin coupling, particularly between fluorine-19 nuclei, provides valuable structural information.
- Previous experimental studies on peri-difluoronaphthalene highlighted a significant anisotropic contribution to the four-bond fluorine-fluorine coupling.
Purpose of the Study:
- To perform first-principles electronic structure calculations of nuclear magnetic resonance (NMR) spin-spin coupling tensors for the fluorine-19 nucleus in peri-difluoronaphthalene.
- To theoretically investigate and confirm the experimentally observed anisotropic contribution to the four-bond fluorine-fluorine coupling.
- To calculate all coupling tensors involving fluorine-19 nuclei in the molecule.
Main Methods:
- Utilizing density-functional theory (DFT) with various exchange-correlation functionals.
- Employing polarization-consistent basis sets optimized for J-coupling calculations.
- Applying the second-order polarization propagator approximation (SOPPA) for accurate coupling tensor determination.
Main Results:
- Calculated all spin-spin coupling tensors involving fluorine-19 nuclei in peri-difluoronaphthalene.
- Confirmed the sign and magnitude of the anisotropic part of the four-bond fluorine-fluorine coupling, with theoretical values around -10 Hz compared to experimental -31.6 Hz.
- Identified significant anisotropic contributions in long-range carbon-13-fluorine-19 and proton-fluorine-19 coupling tensors.
Conclusions:
- The quantum chemical calculations successfully reproduce the experimental observations regarding the anisotropic spin-spin coupling in peri-difluoronaphthalene.
- The study validates the use of DFT and SOPPA for predicting NMR spin-spin coupling tensors, including anisotropic effects.
- Significant anisotropic contributions are not limited to F-F couplings but also extend to C-F and H-F couplings in this system.
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