Effect of Chemical Composition of Fullerenes on the Structure and Internal Rotation Barrier of Encapsulated Ammonia Borane Molecule

Resumo

Investigation of the structure and conformational properties of ammonia borane molecule in the cavity of C₆₀, C₁₂B₂₄N₂₄, B₃₆N₂₄, C₇₀, B₄₁N₂₉, C₈₀, C₁₄B₃₃N₃₃, and B₄₇N₃₃ fullerenes using the DFT PBE/3ζ method has shown the predominance of the staggered conformation of the encapsulated molecule. The guest molecule has bared a notable negative charge and, as compared to the free molecule of ammonia borane, has a shortened B←N coordination bond. The internal rotation barrier about this bond has depended on the composition of the fullerene shell so that the decrease in the number of carbon atoms due to the replacement with boron-nitrogen fragments has almost always resulted in a notable decrease in the ΔG^≠₂₉₈ value. In this case, the minimal energy of the activation barrier, 1.3–1.8 times lower than that simulated for the free molecule, has been observed for the clusters with the boron-nitrogen-carbon links in the fullerene shell.