An ab initio and QTAIM study of hydrogen bonded clusters of nitrosyl hydride with ammonia

Ab initio calculations at MP2/6-311++G(d,p) computational level were used to analyze the interaction between a molecule of the nitrosyl hydride with 1 up to 4 molecules of ammonia. Three minima were found for 1:2 and 1:4 complexes of HNO and NH₃. Four complexes were located as minima on the potential energy surface of 1:3 complexes. Particular attention is given to existence and magnitude of NH⋯N blue-shifting hydrogen bonds. Blue shifts of the N–H stretching frequency upon complex formation in the ranges between 33 and 105 cm⁻¹ are predicted. Cooperative effect in terms of stabilization energy is calculated for the studied clusters. The cooperative effect is increased with the increasing size of studied clusters. The Quantum Theory Atoms in Molecules (QTAIM) theory was also applied to explain the nature of the complexes.