Determining Hydrogen Atom Positions for Hydrogen Bonded Interactions: A Distance-Dependent Neutron-Normalized Method

Crystal structures determined by neutron and X-ray diffraction were retrieved from the Cambridge Structural Database (CSD), and hydrogen-bond geometrical descriptors (distances and angles) have been pairwisely compared, confirming that the two techniques produce significantly different results for the determination of hydrogen atom positions. Inclusion of neutron-normalized data shows that normalization fails to correct for bond polarization when applied to H-bond interactions. Statistical analysis has been carried out, and an empirical method is suggested for calculating more accurate positions for the hydrogen atoms involved in hydrogen bond formation. The simplicity of the approach is promising for future implementation in common crystal structure analysis software packages. The results are presented with a view to opening a discussion on how to approach one of the main limitations of X-ray diffraction in the area of structural chemistry.