Interplay between N∙∙∙H, N∙∙∙X and π∙∙∙X interactions in the complex pairing of pyrazine with hypohalous acids: A NBO and QTAIM (quantum theory of atoms in molecules) analysis

A Zabardasti,H Goudarziafshar,Y A Tyula

doi:10.4314/bcse.v31i2.6

Abstract

The theoretical calculations of the complexes formed by pyrazine (PZ) with hypohalous acids (HOX; X= F, Cl, Br and I) have been carried out at the MP2/6-311++G(2d,2p) computational level. PZ and HOX molecules could have three different types of interactions including hydrogen bond (N∙∙∙H) and halogen bonds (N∙∙∙X, p∙∙∙X). The nature of halogen atom has a small effect on the hydrogen bonds, whereas it imposes a great impact on the halogen bond interactions. The strength, properties and nature of interactions were analyzed using natural bond orbital (NBO) and atoms in molecules (AIM) theories. KEY WORDS : Pyrazine, Hypohalous acid, Hydrogen bonding, Halogen bonding, p∙∙∙X interaction Bull. Chem. Soc. Ethiop. 2017 , 31(2), 241-252. DOI: http://dx.doi.org/10.4314/bcse.v31i2.6

Highlights

Noncovalent interactions play an extensive and important role in drug optimization, supramolecular assembly, crystal engineering, reaction selectivity and molecular biology [1,2,3,4]
Harmonic vibrational frequency calculations were used at the same level of theory to identify the local minima structures on the potential energy surfaces and to obtain zero-point vibrational energy (ZPVE)
The natural bond orbital (NBO) method [45] was used to analyze the interaction of the occupied and empty orbitals via procedures contained within Gaussian 03 [46]

Summary

Introduction

Noncovalent interactions play an extensive and important role in drug optimization, supramolecular assembly, crystal engineering, reaction selectivity and molecular biology [1,2,3,4]. A growing amount of experimental and theoretical evidence has demonstrated that halogen bonds (XB) interactions play a key role in a wide variety of chemical systems such as biochemistry and medicinal chemistry [7,8,9]. Because they are often involved in protein-ligand interactions that are either biologically detrimental, as in the case of interactions involving organohalogens found in the environment, or beneficial because of their potential usefulness in the design of novel ligands that interact with proteins in a very specific way [10, 11]. Concerning strength, halogen bonds are comparable to hydrogen bonds and a competition may occur between them, in recent years much attention has been paid to it [9, 15,16,17]

Methods

Results

Conclusion