Can lone pairs bind to a pi system? The water...hexafluorobenzene interaction.

[formula: see text] Ab initio calculations reveal a significant binding interaction between water and hexafluorobenzene in a geometry that points the oxygen lone pairs directly into the face of the pi system. The geometry is as anticipated from electrostatic arguments emphasizing the substantial quadrupole moment of the aromatic. A second, off-axis geometry is also found which is also consistent with a substantial electrostatic interaction.