The hydrogen bond interactions in glycine–nitrosamine complexes: a DFT study

Abstract

The strong and directional hydrogen bonding interaction between glycine (G) and nitrosamine (NA) have been investigated using B3LYP and B3PW91 methods with a wide range of basis sets. With four preferential interaction sites in the vicinity of the glycine, eight different conformations (GNA1-8) with two intermolecular hydrogen bonds [NHNA···N(O)G and O(N)NA···HXG (X = O, N, C)] were found on the potential energy surface. The influence of the hydrogen bond on the molecular and topological properties, as well as nuclear magnetic resonance one- and two-bond spin–spin coupling constants in the gas phase was investigated. The most stable complexes labeled GNA1 and GNA2 are formed in S1 site. Natural bond orbital analysis shows that in the most stable complexes GNA1 and GNA2 the charge transfer takes place from NA to G, whereas, the reverse happens in other complexes. The results predict that in all complexes, the LPO(N)NA → σ*(X–H)Gly (X = O, N, C) and LPN(O)Gly → σ*(N–H)NA donor–acceptor interactions are the most important interactions. Atom in molecule analysis confirms that all hydrogen bonds have partially covalent nature. The covalent nature of proton donor groups decreases upon complexation. The relationship between spin–spin coupling constant (1h JH···Y and 2h JH···Y) with interaction energy and electronic density at corresponding hydrogen bond critical points and H-bonds distances are investigated.