Density functional study of reactivity and regioselectivity of H2O@C60

The exohedral reactivity of endohedral fullerene has aroused significant interest because of its potential applications in biology, medicine and material science. The encapsulation of a single water molecule without any hydrogen bonding to other compounds, inside the hydrophobic environment of C60 is an intriguing topic to study about. In 2011, Kurotobi and Murata successfully synthesized H2O@C60 fullerene. The presence of a polar water molecule inside the cage is expected to cause changes in the exohedral reactivity of C60. In order to find out the impact of an entrapped single water molecule on the reactivity of C60 fullerene, we use density functional theory to study the thermodynamics and kinetics of [4+2] Diels-Alder reaction of 1, 3 cis butadiene at all non-identical bonds of free C60 and H2O@C60. Our calculations show that the encapsulation of a single water molecule does not have any significant effect on the exohedral reactivity compared to free C60. Moreover, the obtained reaction energies and activation barriers indicate that [6, 6] bond is more reactive than [5, 6] bond and thus cycloaddition is clearly favored at [6, 6] bond. The dipole moment of the H2O@C60 is only 0.48 Debye significantly smaller than that of water molecule. The infrared and Raman spectra of the endohedral fullerene are also computed