Assembly of Three Cadmium(II) Complexes Based on Flexible α,ω-Bis(benzimidazolyl)alkane Ligands

Three flexible alpha, omega-bis(5,6-dimethylbenzimidazolyl)alkane ligands with different spacers were reacted with CdX2 (X = Cl, Br, I) hydrothermally, resulting in three coordination architectures, namely [CdI2(L-1)](n) (1), [CdBr2(L-2)(n) (2), and Cd2Cl4(L-3)(2) (3) [L-1 = 1,3-bis(5,6-dimethylbenzimidazole)propane, L-2 = 1,5-bis(5,6-dimethylbenzimidazole)pentane, L-3 = 1,6-bis(5,6-dimethylbenzimidazole)hexane]. They have been characterized by elemental analyses, IR spectra, thermogravimetric (TG) analysis, and single-crystal X-ray diffraction. Complex 1 displays a helical chain linked by the ligands L-1, and a 2D supramolecular network is constructed through pi-pi stacking interactions; complex 2 shows a helical chain structure with connections through two kinds of strong pi-pi stacking interactions into an intricate 3D supramolecular network; complex 3 contains dinuclear metallomacrocycles. The fluorescence properties of 1-3 have been investigated in the solid state.