Hydrogen atom behaviour imaged in a short intramolecular hydrogen bond using the combined approach of X-ray and neutron diffraction

The short intramolecular hydrogen bond in dibenzoylmethane has been studied by variable temperature neutron and X-ray single-crystal diffraction. Fourier difference maps have been used to image both the nuclear and electronic density of the hydrogen bond, in addition to determination of the refined positions obtained from the maxima of these densities. The nuclear density obtained from the neutron diffraction data shows an asymmetric position of the hydrogen atom in the hydrogen bond which is invariant as a function of temperature. The electronic density imaged from X-ray measurements, on the other hand, shows a migration of the bonding density from an asymmetric position at low temperatures to an almost centred position at room temperature