The nature and energy characteristics of intramolecular hydrogen bonds in crystals

The review concerns the results of systematic X-ray diffraction studies of the electron density distribution in the crystals of compounds with strong intramolecular hydrogen bonds N-H center dot center dot center dot O, O-H center dot center dot center dot O, O-H-center dot center dot center dot N, and N-H center dot center dot center dot S. The advantages of the topological analysis of the electron density distribution function in the analysis of the nature and estimation of the H-bond energies directly from experimental data are discussed.