DFT model investigations on copper(II) chloride complexes: Halogen bonding of pyridyl bromine of CuCl2(NH3)(NC5H4Br-3) with several metal ligands

A set of theoretical model systems, investigated by the DFT method with hybrid basis sets, was utilized to mimic and exploit the halogen bond found in the neutral metal-organic coordination, CuCl2(NC5H4Br-3)2. The optimized calculations indicate that, while coordinating to metal ions, the end-bromine of organic halide subunit exhibits better directionality and affinity to electron density donors. Halogen bonding energies are substantial and range from −2.5 to −37.5 kcal/mol. These results reveal the importance of metal-influenced halogen bonding in directing supramolecular arrangements. To further study the nature of the halogen bond, the analyses of NBO and AIM were carried out. The conclusions show a considerable extent of charge transfer, complicated orbital interactions, and distinct bond critical points between interacting atoms upon halogen bonding.