A theoretical perspective of the nature of hydrogen-bond types – the atoms in molecules approach

Abstract

Hydrogen bonds and their strength were analysed based on their X–H proton–donor bond properties and the parameters of the H–Y distance (Y proton acceptor). Strong, moderate and weak interactions in hydrogen-bond types were verified through the proton affinities of bases (PA), deprotanation enthalpies of acids (DPE) and the chemical shift (σ). The aromaticity and anti-aromaticity were analysed by means of the NICS (0) (nucleus-independent chemical shift), NICS (1) and ΔNICS (0), ΔNICS (1) of hydrogen-bonded molecules. The strength of a hydrogen bond depends on the capacity of hydrogen atom engrossing into the electronegative acceptor atom. The correlation between the above parameters and their relations were discussed through curve fitting. Bader's theory of atoms in molecules has been applied to estimate the occurrence of hydrogen bonds through eight criteria reported by Popelier et al. The lengths and potential energy shifts have been found to have a strong negative linear correlation, whereas the lengths and Laplacian shifts have a strong positive linear correlation. This study illustrates the common factors responsible for strong, moderate and weak interactions in hydrogen-bond types.

Keywords:

• hydrogen bond
• proton affinity
• deprotanation enthalpy
• atoms in molecules
• chemical shift

Acknowledgements

Dr P. Deepa expresses her sincere thanks to Prof. Pavel Hobza and the Research Project RVO: 61388963 of the Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic for its support. We thank Dr A.K. Chandra, Department of Chemistry, North Eastern Hill University, Shillong, India, and Prof. E. Arunan, Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, for their help in some of the discussion of the results presented in the paper.