Effect of confinement on ammonia inversion

Abstract

The effect of confinement on ammonia inversion inside C50 (D 5h ) and C60 (I h ) fullerenes has been investigated. Calculations at the DFT(M06-2X)/6-311G** level of theory suggest that NH3 is stable inside both C50 and C60 by −8.6 and −23.8 kcal mol −1 , respectively. While the barrier for inversion of the free NH3 molecule is estimated to be 1896 cm −1 , it increases to 1972 cm −1 and 2108 cm −1 , respectively, inside C50 and C60. The results also reveal that the magnitude of splitting of the bound states below the barrier in the symmetric double-well potential decreases inside both the C50 and C60 cages.

Improved Estimates of Host‐Guest Interaction Energies for Endohedral Fullerenes Containing Rare Gas Atoms, Small Molecules, and Cations

“…For the NH 3 molecule, Mallick et al. predicted a redshift in NH 3 , supported by previous experimental results [75] . Among the small molecules considered here, only CH 4 exhibits a blueshift, which is in agreement with the previous findings [45,69] …”

“…In the DFT(MN15)/cc‐pVTZ optimized geometry of the complexes, the bond lengths of small molecules (H 2 , HF, H 2 O and NH 3 ) are found to be slightly increased, compared to those of the free molecules, as shown in Table 5. The bond lengths of H−H, H−F, O−H and N−H are increased by 0.0100, 0.0098, 0.0071 and 0.0046 Å, respectively, which coincides well with previous theoretical reports for HF, [14,37,65] H 2 O [22,33,48] and NH 3 [38,75] . On the other hand, there is a slight decrease of 0.001 Å for the C−H bond length of CH 4 inside the cage, when compared to that of free CH 4 , in agreement with the previous predictions [45,47,48] .…”

“…The bond lengths of HÀ H, HÀ F, OÀ H and NÀ H are increased by 0.0100, 0.0098, 0.0071 and 0.0046 Å, respectively, which coincides well with previous theoretical reports for HF, [14,37,65] H 2 O [22,33,48] and NH 3 . [38,75] On the other hand, there is a slight decrease of 0.001 Å for the CÀ H bond length of CH 4 inside the cage, when compared to that of free CH 4 , in agreement with the previous predictions. [45,47,48] Furthermore, Table 5 lists the stretching ChemPhysChem frequencies corresponding to the YÀ H bond of the small molecules, with the Δν shifts caused by encapsulation.…”

External electric field to control the Diels–Alder reactions of endohedral fullerene

“…6,7 In addition, properties of fullerene can also be modified by encapsulating atoms, molecules and metal clusters; known as endohedral fullerenes. [8][9][10][11][12][13] Among the various size of fullerenes, the most representative member is C 60 . Similar to benzene, C 60 is also electron-deficient and hence can be easily functionalized through various cycloaddition reactions such as Diels-Alder, Bingel-Hirch, 1-3 dipolar, etc.…”