Controllable Supramolecular Assembly by π−π Interactions: Cobalt(II) and Copper(II) Complexes with Benzimidazole Derivatives

Two novel helical supramolecular architectures were constructed by self-assembly of cobalt(II) (1) and copper(II) complexes (2) of 1-[(5-methyl-2-furyl)methylene]-2-(5-methyl-2-furyl)benzimidazole in the crystalline form, which were stabilized through the intra- and
intermolecular π−π interactions between benzimidazole rings. When the methylfuran
fragment of the ligand was switched to a furan group, the cobalt complex (3) of 1-(2-furylmethylene)-2-(2-furyl)benzimidazole formed another type of supramolecular network
through π−π interactions under similar reaction conditions. The spectral and thermal
behaviors of complexes 1−3 were investigated by ultraviolet, chiral dichroism, and
fluorescence spectral and thermogravimetric techniques. When MAO was used as the
cocatalyst, complex 1 displayed satisfactory activity for ethylene oligomerization up to 2.5
× 105 g of C2H4 mol-1 h-1 at room temperature and 9 atm of ethylene.