Halogen bonds involving an aromatic moiety as an acceptor, otherwise known as R-X…π interactions, have increasingly been recognized as being important in materials and in protein-ligand complexes. These types of interactions have been the subject of many recent investigations, but little is known about the ways in which the strengths of R-X…π interactions vary as a function of the relative geometries of the interacting pairs. Here we use the accurate CCSD(T) and SAPT2+3δMP2 methods to investigate the potential energy landscapes for systems of HBr, HCCBr, and NCBr complexed with benzene. It is found that only the separation between the complexed molecules have a strong effect on interaction strength while other geometric parameters, such as tilting and shifting R-Br…π donor relative to the benzene plane, affect these interactions only mildly. Importantly, it is found that the C6v (T-shaped) configuration is not the global minimum for any of the dimers investigated.
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