A series of six mononuclear Cu(II) complexes with pyrazole-based ligands: 5-(2-hydroxybenzoyl)-3-methyl-1-(2-pyridinyl)-1H-pyrazol-4-phosphonic acid dimethyl ester (1a), 5-(2-hydroxyphenyl)-3-methyl-1-(2-pyridylo)-1H-pyrazole-4-carboxylic acid methyl ester (1b) and 1-benzothiazol-2-yl-5-(2-hydroxyphenyl)-3-methyl-1H-pyrazole-4-carboxylic acid methyl ester (1c) were characterized regarding to electrochemical and antioxidant properties. All complexes exhibit suitable Cu(II)/Cu(I) redox potential (E (1/2)) to act as antioxidant enzymes mimic. The five of these complexes were found to be trifunctional enzyme mimics possessing SOD, CAT and GPx-like catalytic activities. Moreover, Cu(II) complexes were capable to decrease ROS level in melanoma cells and observed effects were not merely a reflection of cytotoxicity.
Synthesis, X-ray structures, electrochemical properties and cytotoxic effects of Co(II) complexes
1-Benzothiazol-2-yl-3,5-dimethyl-1H-pyrazole (1a) and 1-benzothiazol-2-yl-5-(2-hydroxyphenyl)-3-methyl-1H-pyrazole-4-carboxylic acid methyl ester (1b) were reacted with the hexahydrates of cobalt(II) chloride, cobalt(II) nitrate and cobalt(II) perchlorate to give the corresponding complexes 2a-4a and 2b-5b, respectively. Obtained compounds differ in coordination spheres of central atoms. The complex 2a includes a fivefold coordinated cobalt(II) ion, whereas 3a shows a distorted octahedral configuration around the cobalt(II) ion. All complexes were characterised by FTIR spectroscopy, MS and elemental analysis. The X-ray structures of 2a, 3a and 5b complexes were also solved. The cytotoxic properties of the ligand 1a and both series of Co(II) complexes were examined on human leukemia NALM-6 and HL-60 cells and melanoma WM-115 cells. The ligands, were found to have very low cytotoxicity. Complex 3b exhibited the highest cytotoxic activity with IC50 values in the range of 6.9-17.1 mu M for three examined cell lines. (C) 2010 Elsevier B.V. All rights reserved.