The shortest symmetrical O-H...O hydrogen bond has a low-barrier double-well potential

The comprehensive crystallographic, NMR and spectroscopic data reveals a united and a self-consistent picture of a symmetrical molecule with a low-barrier hydrogen-bond. The temperature dependence of the NMR properties confirms the existence of a thermally accessible vibrationally excited state for the bond and as other short hydrogen bonds show similar NMR behavior, it is likely the no 'strong' hydrogen bond of this sort has yet been discovered.