Zinc(II) and mercury(II) coordination architectures with two pyridyl/benzimidazol-1-yl-based ligands: Crystal structures and photoluminescent properties

In our efforts to investigate the relationships between the structures of ligands and their complexes, two structurally related ligands, 1-(2-pyridylmethyl)-1H-benzimidazole (L1) and 1-(4-pyridylmethyl)-1H-benzimidazole (L2), and their four complexes, [Zn(L1)2Cl2] (1), [Hg(L1)Br2]∞ (2), {[Zn(L2)Cl2](CH3CN)}∞ (3) and [Hg(L2)Br2]2(CH3CN)2 (4) were synthesized and structurally characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction analysis. Structural analyses show that 1 has a mononuclear structure, and 2 and 3 both take 1D structure. While 4 takes a dinuclear structure. 1, 2 and 4 were further linked into higher-dimensional supramolecular networks by weak interactions, such as C–H⋯Cl and C–H⋯Br H-bonding, C–H⋯π, and π⋯π stacking interactions. The structural differences of 1–4 may be attributed to the difference of the spatial positions of the terminal N donor atoms in the pendant pyridyl groups in L1 and L2, in which the pyridine rings may act as the directing group for coordination and the benzimidazole rings act as the directing group for π⋯π stacking and C–H⋯π interactions. The luminescent properties of the corresponding complexes and ligands have been further investigated.