Synthesis, crystal structures, and properties of copper(II) complexes with 2,6-bis(benzimidazol-2-yl)pyridine

Three new mononuclear copper(II) complexes, [CuL(2-fca)(CH(3)OH)]ClO(4) center dot CH(3)OH (1), [CuL(m-nba)(CH(3)OH)]ClO(4) (2), and [CuL(pic)(ClO(4))] center dot CH(3)OH (3), were synthesized and structurally characterized, where L is 2,6-bis(benzimidazol-2-yl) pyridine, while 2-fca, m-nba, and pic are the anions of 2-furoic acid, m-nitrobenzoic acid, and picolinic acid, respectively. All of them were characterized by elemental analysis, infrared, UV-Vis, and X-ray crystallography. In 1 and 2, the Cu(II) resides within a distorted square-pyramidal N(3)O(2) coordination sphere with three nitrogens of L, one carboxylate oxygen, and one methanol. In 3, Cu(II) is coordinated with three nitrogens of L, one nitrogen and one oxygen of picolinate, and one oxygen of perchlorate in a distorted octahedral geometry. Two molecules of 1, 2, and 3 are interacted by intermolecular hydrogen-bonding interactions and strong pi-pi stacking interactions to form a dinuclear structural unit. The dinuclear units are further connected by H-bonds via perchlorate or lattice methanol to form a 1-D chain for 1 and 2-D network structures for 2 and 3. Hydrogen-bonding and pi-pi stacking interactions are important for the stabilization of the final supramolecular structures of the three complexes.