Effect of anions on cadmium(II) complexes with ligand 2-(pyrazin-2-yl)-1H-benzimidazole

Abstract

Three new supramolecular complexes based on a 2-(pyrazin-2-yl)-1H-benzimidazole (Hpbi) and a series of Cd(II) salts have been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of CdCl2·2.5H2O with Hpbi afforded a one-dimensional chain [Cd(Hpbi)Cl2] (1), which exhibits a three-dimensional (3-D) supramolecular architecture through intermolecular X–H···Cl (X=N and C) hydrogen bonds and π–π stacking interactions. When using CdBr2·4H2O instead of CdCl2·2.5H2O under similar reaction conditions, a bisnuclear complex [Cd(Hpbi)2Br2] (2) is obtained, which obviously exhibits intermolecular X–H···Br (X=N and C) hydrogen bonds and π–π stacking interactions. When CdI2 take place of CdCl2·2.5H2O, a mononuclear complex, [Cd(Hpbi)2I2] (3), is isolated, which shows a 3D supramolecule framework formed by intermolecule hydrogen bonds and π–π packing interactions. Interestingly, the Hpbi ligand exhibits the same coordination modes in complexes 1–3. It is noteworthy that the radius of anions plays an important role in affecting the structures and luminescent intensity of the final products. The TGA for 1–3 have been investigated and discussed in detail.