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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
Discriminating the structure of exo-2-aminonorbornane using nuclear quadrupole coupling interactions
Patricia Écija1, Emilio J Cocinero, Alberto Lesarri
1Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV-EHU), Ap. 644, 48080 Bilbao, Spain.
The Journal of Chemical Physics
|May 3, 2011
Summary
Exo-2-aminonorbornane conformations were studied using microwave spectroscopy and quantum calculations. Two stable forms were identified, with the most stable having staggered amino N-H bonds, revealing insights into molecular structure.
Area of Science:
- Molecular spectroscopy
- Quantum chemistry
- Structural analysis
Background:
- Understanding the conformational landscape of bicyclic molecules is crucial for predicting their chemical behavior.
- Exo-2-aminonorbornane presents unique structural challenges due to its bicyclic nature and the amino group's rotational freedom.
Purpose of the Study:
- To investigate the intrinsic conformational and structural properties of exo-2-aminonorbornane.
- To identify and characterize different conformers using experimental and computational methods.
- To elucidate the role of the amino group's internal rotation in determining molecular structure.
Main Methods:
- Fourier-transform microwave (FT-MW) spectroscopy in a supersonic jet expansion.
- Ab initio (MP2) and Density Functional Theory (DFT) quantum chemical calculations (B3LYP, M05-2X).
- Analysis of rotational spectra, nuclear quadrupole coupling (14N), and conformational dependence of hyperfine tensors.
Main Results:
- Two distinct conformers of exo-2-aminonorbornane were detected via rotational spectroscopy.
- The most stable conformer (ss) features staggered amino N-H bonds relative to adjacent C-H bonds.
- A third predicted conformer (ts) was not observed, likely due to low isomerization barrier to the most stable form.
Conclusions:
- The study successfully characterized the conformational preferences of exo-2-aminonorbornane.
- Nuclear quadrupole coupling was key in assigning structures due to similar rotational constants.
- Conformational relaxation pathways and energy barriers were elucidated, providing a comprehensive understanding of this bicyclic amine.
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