Self‐Assembly, Spectroscopic and Electrochemical Studies of Nickel(II)‐4,8‐Diazaundecanediamide Complex

The self-assembly of NiCl(2 center dot)6H(2)O with a diaminodiamide ligand 4,8-diazaundecanediamide (L-2,3,2) gave a [Ni(C9H20N4O2)(Cl)(H2O)]Cl center dot 2H(2)O (1). The structure of 1 was characterized by single-crystal X-ray diffraction analysis. Structural data for 1 indicate that the Ni(II) is coordinated to two tertiary N atoms, two 0 atoms, one water and one chloride in a distorted octahedral geometry. Crystal data for 1: orthorhombic, space group P 21nb, a = 9.5796(3) angstrom, b = 12.3463(4) angstrom, c = 14.6305(5) angstrom, Z = 4. Through NH center dot center dot center dot Cl-Ni (H center dot center dot center dot Cl 2.42 angstrom, N center dot center dot center dot Cl 3.24 angstrom, NH center dot center dot center dot Cl 158 degrees) and OH center dot center dot center dot Cl-Ni contacts (H center dot center dot center dot Cl 2.36 angstrom, O center dot center dot center dot Cl 3.08 angstrom, OH center dot center dot center dot Cl 143 degrees), each cationic moiety [Ni(C9H20N4O2)(Cl)(H2O)](+) in 1 is linked to neighboring ones, producing a charged hydrogen-bonded 1D chainlike structure. Thermogrametric analysis of compound 1 is consistent with the crystallographic observations. The electronic absorption spectrum of Ni(L-2,3,2)(2+) in aqueous solution shows four absorption bands, which are assigned to the (3)A(2)g -> (3)T(2)g, (3)A(2)g -> (1)Eg, (3)A(2)g -> (3)T(1)g, and (3)A(2)g -> (3)T(1)g transitions of triplet-ground state, distorted octahedral nickel(II) complex. The cyclic volammetric measurement shows that Ni2+ is more easily reduced than Ni(L-2,3,2)(2+) in aqueous solution.