Comparative insight into the halogen bonding of 4-chloropyridine and its metal [CuI,ZnII] coordinations with halide ions: A theoretical study on M–C–X⋯X′

The M–C–X⋯X′ halogen bond may be considered as a novel supramolecular synthon for prediction and design of polymeric metal frameworks. In this work, a set of theoretical models, consisting of two series of complexes PyCl⋯X (PyCl=NC5H4Cl-4; X=F−, Cl−, or Br−) and MPyCl⋯X (M=Cu+, Zn2+), was utilized to reveal features of M–C–X⋯X′. To explore the influence of metal centers, a detailed comparison of the properties in PyCl⋯X and MPyCl⋯X complexes was carried out. The results showed that, while coordinating to metals, interaction energies and charge transfers exhibit a remarkable increase, which have been rationalized by analyses of electrostatic potential and density difference function. Furthermore, the individual energy contributions were examined through the symmetry-adapted perturbation theory, and the results indicated that the dominant energy contribution emerges from the electrostatic and induction energy, and the electrostatic term presents a higher increment than other energy components.