科研之友
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摘要
We have performed a density functional study to investigate the structural and magnetic properties of full equatorial BN-substituted fullerenes and nanocapsules C-20(BN) (m) , m = 15, 25, 35, 45 and 55, in comparison to their parent cages C (n) , n = 50, 70, 90, 110, 130, with D (5h) symmetry. Binding energies for the BN substituted nanocages C-20(BN) (m) are lower than those of their parents, generally increasing as the size of tubular belt increases. According to the computed nucleus independent chemical shifts (NICS) along principal axes, different behaviors of magnetic field are detected inside the tubular belts of nanocages. First, the substitution of BN units for CC ones in fullerenes (n = 50, 70, 90) results in less negative NICS at the cage centers, less aromaticity, in comparison to their parent fullerene; however NICS at the cage centers of the BN-substituted nanocapsules (n = 110, 130) are more negative than pure carbon nanocapsules, more aromaticity. Second, the full equatorial BN substitution of nanocapsules leads to a homogeneous magnetic field, while dramatic changes in local ring currents cause a sharp maximum in the NICS plots of the pure carbon compounds. Finally, the presence of the caps bonded to BN tubular parts significantly affects electron delocalization and consequently induces aromaticity to these compounds.
- 出版日期2014-7
