Cooperativity between the hydrogen bonding and σ-hole interaction in linear NCX•••(NCH)n=2-5 and O3Z•••(NCH)n=2-5 complexes (X = Cl, Br; Z = Ar, Kr): a comparative study

Quantum chemical calculations are performed to investigate the cooperativity of hydrogen bonding with halogen or aerogen bonding interactions in linear NCX center dot center dot center dot(NCH)(n=2-5) and O(3)Z center dot center dot center dot(NCH)(n=2-5) clusters, where X = Cl, Br and Z = Ar, Kr. To understand the cooperativity mechanism in these systems, the corresponding binary NCX center dot center dot center dot NCH and O(3)Z center dot center dot center dot NCH complexes are also considered. The binding distances, interaction energies, and bonding properties of the NCX center dot center dot center dot(NCH)(n=2-5) and O(3)Z center dot center dot center dot(NCH)(n=2-5_)clusters are analyzed in detail. It is found that the cooperative effects in the hydrogen bonding tend to strengthen X center dot center dot center dot N and Z center dot center dot center dot N interactions. For both NCX center dot center dot center dot(NCH)(n) and O(3)Z center dot center dot center dot(NCH)(n) clusters, a small bond shrinkage is observed from n = 4 to n = 5, which suggests that the cooperativity effects are almost saturated in the larger clusters (n > 5). As the size of the X or Z atom is increased, the magnitude of the cooperative energy in these systems is also increased, which is mainly ascribed to changes in electrostatic potentials and orbital interactions. Our results indicate that the cooperative effects lead to a substantial change in the N-14 nuclear quadrupole coupling constants of the NCH molecule.