Synthesis, structure and antitumor activities of a new macrocyclic ligand with four neutral pendent groups: 1,4,7,10-tetrakisbenzyl-1,4,7,10-tetraazacyclododecane (L) and its Co, Ni and Cu complexes

A new macrocyclic ligand, 1,4,7,10-tetrakisbenzyl-1,4,7,10-tetraazacyclododecane (L) and its three new divalent metal complexes of general formula: M(NO3)(2)(L)nH(2)O [M = Co(1), Ni(2), n = 0; M = Cu(3), n = 1.5] have been synthesized and characterized by elemental analysis, i.r., EI mass spectra and molecular conductance. Complex (2) has been characterized by X-ray diffraction. In complex (2), the central (NiI)-I-I atom coordinatively bonds to four nitrogen atoms of the macrocyclic ligand and two oxygen atoms of nitrate anion, to form a distorted octahedron. X-ray diffraction indicated that the bonds Ni-N(1), Ni-N(2), Ni-N(3) and Ni-N(4) are of almost equal length, i.e. 2.11(1), 2.12(1), 2.10(1) and 2.17(1) Angstrom, respectively. Bond lengths of Ni-O(1) and Ni-O(2) are 2.11(1) and 2.10(1) Angstrom. Preliminary pharmacological tests show that these complexes have high antitumor activity towards HL-60 tumor cell lines.