Theoretical investigation of equilibrium and transition state structures, binding energies and barrier heights of water-encapsulated open-cage [59]fullerenone complexes

The encapsulation of a water molecule within two open-cage [59]fullerenones with 18-membered-ring (1) or 19-membered-ring orifices (2) is studied by DFT with empirical dispersion terms. The equilibrium structure of each H2O@[59]fullerenone and the transition-state structure for the water molecule leaving the cage are optimised and the counterpoise-corrected binding energy and barrier height are calculated. While the H2O binding energies in H2O@1 and H2O@2 are almost equal, the barrier for H2O leaving the cage is much higher for 1 (108 kJ mol−1) than for 2 (46 kJ mol−1). A water molecule can enter the cage-opened fullerenone 2 almost barrierless, whereas this barrier is 63 kJ mol−1 in 1.