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Formation, isolation, spectroscopic properties, and calculated properties of some isomers of C(60)H(36)
J Nossal1, R K Saini, A K Sadana
1Department of Chemistry, Rice University, Houston, TX 77005, USA.
Journal of the American Chemical Society
|August 30, 2001
Summary
Researchers synthesized and analyzed isomers of C(60)H(36) using NMR spectroscopy and DFT calculations. They identified specific isomers and investigated unusual NMR signal deshielding, linking it to molecular structure.
Area of Science:
- Fullerenes chemistry
- Supramolecular chemistry
- Organic synthesis
Background:
- Fullerenes, such as C(60), are carbon allotropes with unique electronic and structural properties.
- Functionalization of fullerenes, like C(60)H(36), leads to diverse isomers with varied properties.
- Understanding the structure-property relationships of fullerene derivatives is crucial for their applications.
Purpose of the Study:
- To synthesize and characterize isomers of C(60)H(36) and their endohedral helium complexes (He@C(60)H(36)).
- To assign structures of synthesized isomers using NMR spectroscopy and computational methods.
- To investigate the factors contributing to unusual NMR chemical shifts in C(60)H(36) isomers.
Main Methods:
- Synthesis of C(60)H(36) isomers via Birch or dihydroanthracene reduction of C(60).
- Isolation of isomers using preparative high-pressure liquid chromatography (HPLC).
- Characterization using Nuclear Magnetic Resonance (NMR) spectroscopy ((3)He, (13)C, (1)H) and Density Functional Theory (DFT) calculations.
Main Results:
- Several isomers of C(60)H(36) and He@C(60)H(36) were synthesized and isolated.
- NMR data, compared with DFT calculations (B3LYP), allowed provisional structural assignments for some isomers.
- The dihydroanthracene reduction method yielded specific isomers, suggesting they are minor products of Birch reduction.
- Unusually deshielded (1)H NMR signals were observed, correlated with specific structural features like long C-C bonds beta to benzene rings.
Conclusions:
- The study provides insights into the structural diversity and characterization of C(60)H(36) isomers.
- DFT calculations are valuable tools for assigning fullerene isomer structures.
- The observed NMR signal anomalies are linked to the unique electronic environment and bonding in these fullerene derivatives.
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