Comparison of hydrogen bonds, halogen bonds, C-H•••π interactions, and C-X •••π interactions using high-level ab initio methods

High quality CCSD(T) and DFT-SAPT potential energy curves were generated for complexes of HCN, BrCN, and HBr donors with formaldehyde and benzene acceptors in order to compare the strengths and properties of hydrogen bonds, halogen bonds, C-H center dot center dot center dot pi interactions, and C-Br center dot center dot center dot interactions. It is found that interactions involving BrCN, which has a large region of positive charge, are similar in strength to interactions involving HCN. Dispersion plays a pronounced role in Y-Br Tr complexes, accounting for about two thirds of attraction in the HBr C6H6 complex. As might be expected, interactions involving halogens have stronger contributions from dispersion. (C) 2015 Elsevier B.V. All rights reserved.