On the polarity of buckminsterfullerene with a water molecule inside.

Since the recent achievement of Kurotobi and Murata to capture a water molecule in a C(60) fullerene (Science 2011, 333, 613), there has been a debate about the properties of this H(2)O@C(60) complex. In particular, the polarity of the complex, which is thought to be underlying the easy separation of H(2)O@C(60) from the empty fullerene by HPLC, was calculated and found to be almost equal to that of an isolated water molecule. Here we present our detailed analysis of the charge distribution of the water-encapsulated C(60) complex, which shows that the polarity of the complex is, with 0.5 ± 0.1 D, indeed substantial, but significantly smaller than that of H(2)O. This may have important implications for the aim to design water-soluble and biocompatible fullerenes.