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

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.