Synthesis, X-ray structures, properties and SOD-like activity of ternary copper(II) complexes showing the N4O2 coordination with a combination of monodentate and bidentate N-donor ligands

A series of novel copper(II) complexes with the composition of [Cu(H2O)2(L1–5)2(phen)]·2MeOH (1–5), where HL1 = 6-(2-fluorobenzylamino)purine, HL2 = 6-(3-fluorobenzylamino)purine, HL3 = 6-(4-fluorobenzylamino)purine, HL4 = 6-(2-chlorobenzylamino)purine, HL5 = 6-(3-chlorobenzylamino)purine, phen = 1,10-phenanthroline, was synthesized and characterized by elemental analysis, electronic and infrared spectroscopy, magnetic and conductivity measurements. Single-crystal X-ray analysis of complexes 1–4 showed the distorted octahedral geometry in the vicinity of the copper(II) atom, which is coordinated by four nitrogen atoms (two from the bidentate phen ligand and the other two from monodentate 6-(benzylamino)purine derivatives) and two oxygen atoms from the aqua ligands, which together form the N4O2 donor set. The antiradical activity of the prepared complexes was tested by an in vitro SOD-like assay. The IC50 values were found ranging between 104 and 146 μM, which represents ca. 0.5% of the native bovine Cu, Zn-SOD effect.