Synthesis, stability and structural characterization of a new macrocyclic ligand with four neutral pendent groups: 1,4,7,10-tetrakisbenzyl-1,4,7,10-tetraazacyclo dodecane (L) and its Co and Cu complexes

Two new divalent metal complexes of general formula: M(NO3)2(L)nH2O [M=Co (1), n=0; M=Cu (2), n=2] which coordinated to a new macrocyclic ligand, 1,4,7,10-tetrakisbenzyl-1,4,7,10-tetraazacyclododecane (L) have been synthesized and characterized structurally by X-ray diffraction. In complex 1, the central Co atom coordinately bonds to four nitrogen atoms of the macrocyclic ligand and two oxygen atoms of a nitrate anion, to form a slightly distorted octahedron. X-ray diffraction indicated that the bonds lengths of Co–N(1) and Co–N(2) are 2.212(7), 2.230(7) Å, respectively. Bond lengths between Co and two oxygen atoms are the same: Co–O(1) 2.142(7) Å. In complex 2 four nitrogen atoms of macrocyclic ligand coordinated to copper atom together with an oxygen atom from water molecule, which defined a five-coordinated tetragonal pyramid. The distances between Cu and nitrogen atoms are Cu–N(1) 2.020(7) Å and Cu–N(2) 2.030(6) Å, respectively. The bond length of Cu–O(1) is 2.126(6) Å. Potentiometric measurements were determined in 1,4-dioxane–water for L, Co and Cu complexes with the formation constants: log K[ML]=19.79 for Co and 15.61 for Cu.