Estimation of resonance assisted hydrogen bond (RAHB) energies using properties of ring critical points in some dihydrogen-bonded complexes

Abstract

Intramolecular hydrogen bond (IHB) interactions have investigated in aza-boron-hydrogen rings after formation of dihydrogen bond (DHB) interactions with some substituted aza-boron-hydrogen molecules. These molecules include electron-donating and electron-withdrawing groups. The IHB energies in the dihydrogen-bonded complexes have estimated using a method based on properties of ring critical points (RCPs). There is linear relationship between results of this method and molecular tailoring approach (MTA). Geometrical parameters, spectroscopic information, electronic properties based on atoms in molecules (AIM) method, and natural bond orbital (NBO) analysis have used to find effects of DHB on strength of the IHB interaction. Moreover, aromaticity of resonance-assisted hydrogen bond (RAHB) rings have evaluated using the para delocalization index (PDI), the aromatic fluctuation index (FLU), the average two center index (ATI), and the nucleus-independent chemical shift (NICS) to find relation between π-electron delocalization (π-ED) and properties of these rings. Results show that DHB leads to increase of strength of the IHB interaction. In addition, the PDI benchmark has the best correlation with the IHB descriptors. Additionally, localized molecular orbital energy decomposition analysis (LMO-EDA) reveals that the key components of interaction energies are exchange and electrostatic energy, respectively. Finally, new relations obtained for estimation of the IHB energies based on RCP characteristics and quantum mechanical descriptors.