Using neutrons and X-rays to study the effect of temperature on the short hydrogen bond in potassium hydrogen phthalate

Potassium hydrogen phthalate has been investigated at several temperatures by both neutron and X-ray single crystal diffraction methods. Previous studies have shown that medium-to-strong hydrogen bonds will frequently undergo changes in the behaviour of the hydrogen atom as temperature is increased. Observed effects include proton migration and disorder over two positions. No evidence for either effect is observed for the short hydrogen bond in potassium hydrogen phthalate between 30 and 300 K, in either the X-ray or neutron data. In addition to demonstrating the robust nature of the geometry of this interaction with respect to temperature, the study has shown once again that X-ray diffraction coupled with simple Fourier imaging methods can reliably screen such hydrogen bonds.