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 × 10 5 g of C 2 H 4 mol - 1 h - 1 at room temperature and 9 atm of ethylene.