Bis(2‐methylbenzimidazolyl)amine‐Derived Copper Complexes and Their Antineoplastic Activity

Abstract

Abstract Copper(II) complexes ( 1 – 4 ) of tri‐ or tetradentate bis(2‐methylbenzimidazolyl)amine ligands ( L 1 – L 4 ) have been prepared and characterized by spectroscopic methods in solution, as well as in the solid state by X‐ray crystallography. The ligands act as tridentate donors towards the cupric ions through one central amine and two benzimidazole N atoms in the solid state; a water ligand and a bridging perchlorate group define the distorted octahedral environments of 2 and 3 . Complex 4 has square‐pyramidal coordination geometry, with an additional thioether donor attached to the central N atom in the axial position. Electrospray mass spectrometry characterized the complexes as monomeric in acetonitrile solution. Cyclic voltammetry studies established that amine N benzyl‐containing 3 has the highest half‐wave redox potential of all of these complexes at –0.08 V (vs. Fc + /Fc) for the Cu 2+ /Cu + couple. The complexes display dose‐dependent cytotoxicity against one human and four murine cancer cell lines. Complexes 3 and 4 have good antiproliferative activity against the human chronic leukemia cell line K562. Moreover, for 3 the proliferation of all malignant cell lines decreases at concentrations lower than the IC 50 for healthy bone marrow cells.