Synthesis, Structure and Cyclic Voltammetry Studies of a 2D Sheet-like μ3-Hydroxyl- and μ2-, μ4-Oxamidato-Bridged Copper(II) Complex

A novel 2D sheet-like copper(II) complex formulated [Cu6(trans-oxen)3(μ3-OH)2(H2O)2]n-(ClO4) 4n . 2nH2O (1), where H2oxen is N,N’-bis(2-aminoethyl)oxamide, has been synthesized and characterized by elemental analysis, IR and UV–visible spectroscopy, and single-crystal X-ray diffraction. 1 crystallizes in triclinic space group P-1 with crystallographic data: a = 10.299(2) A, b = 10.833(2) A, c = 11.781(2) A, α = 69.95(3)°, β = 81.10(3)°, γ = 62.44(3)°, and Z = 2. In the crystal structure, the cation [Cu6(trans-oxen)3(μ3-OH)2(H2O)2] n 4n+ exhibits a two-dimensional sheet-like structure for Cu(II) ions bridged both by trans-oxen and hydroxyl groups. Each Cu(II) ion is located in a slightly distorted square-pyramidal environment. The hydroxyl group bridges three [Cu(oxen)Cu]2+ dications in which one oxen2− is μ2-bridge while the other two act as never before reported μ4-bridge. Perchlorate anions and H2O molecules are inserted between the sheets and bridge the 2D cations via N–H···O and O–H···O hydrogen bonds to form an infinite three-dimensional system. The cyclic voltammetric behavior of 1 and the influence of counter ions on structure are preliminarily investigated.