Computational study of hydrogen bonding interaction between formamide and nitrosyl hydride

Abstract

The hydrogen bonding interaction of formamide–nitrosyl hydride complex has been investigated using density functional theory (DFT) and ab initio method. The natural bond orbital (NBO) analysis and atom in molecules (AIM) theory were applied to understand the nature of the interaction. Two stable geometries are found on the potential energy surface, a six-membered cyclic structure of complex A and a seven-membered cyclic structure of complex B, characterized by AIM analysis. Complex A is less stable than complex B. It is confirmed that there are contractions of C H (compared with the monomer HCONH 2), N H bonds (compared with the monomer HNO) and the corresponding stretching vibrational frequencies are blue-shifted, while there is an elongation of the N H bond and the corresponding stretching vibrational frequency is red-shifted, relative to those of the monomer HCONH 2. From NBO analysis, it is evident that the electron densities in the σ ∗ (C H) and σ ∗(N H) of the complex A are less than those of the monomers HCONH 2 and HNO, which strengthen C H and N H bonds. Furthermore, the increases in s-characters of X also strengthen X H bonds.