Impact of halogenation and substituent position on supramolecular assemblies of mercury(II) complexes with halogenated imine ligands

چکیده مقاله

In this investigation, a series of mercury(II) coordination complexes containing 3-chloro-N-(pyridin-3-ylmethyl)aniline (3Cl-Py), 3-bromo-N-(pyridin-3-ylmethyl)aniline (3Br-Py), 3-iodo-N-(pyridin-3-ylmethyl)aniline (3I-Py), and 4-iodo-N-(pyridin-3-ylmethyl)aniline (4I-Py) ligands were prepared, varying in the type and position of the halogen atom. These complexes were synthesized to investigate the role of halogen bonding interactions in inorganic supramolecular chemistry. Eight coordination complexes in total were obtained: [HgCl₂(3Cl-Py)]_n, 1, [HgI₂(3Cl-Py)]_n, 2, [HgCl₂(3Br-Py)₂], 3, [HgCl₂(3I-Py)₂], 4, [HgBr₂(3I-Py)₂], 5, [HgI₂(3I-Py)]_n, 6, [HgBr₂(4I-Py)₂], 7, and [HgI₂(4I-Py)]_n, 8. These were synthesized under slow evaporation conditions from mixtures of mercury(II) halides and the respective imine ligands in various solvents. The resulting networks exhibit diverse structures and coordination modes around the metal centers. Compounds 1, 2, 6, and 8 possess one-dimensional (1D) polymeric structures, while 3, 4, 5, and 7 exhibit discrete structures. Initial examination of cell parameters, atomic positions, and crystal packing of complexes 3, 4, and 5 indicates that these compounds are isostructural. The cell unit dissimilarity index of these three compounds was calculated to quantify the degree of similarity. Packing analysis of these compounds clearly shows that in complexes 1, 3, 4, and 5, the halogen atom is involved in non-classical C-H…X hydrogen bonding, whereas complexes 6 to 8 have a significant contribution of I...X halogen bonding (X = Br, I). Finally, the presence or absence of halogen interactions in these complexes was compared with that in previously reported homologous complexes. © 2025 Elsevier B.V.