Synthesis, X-ray structures, electrochemical properties and cytotoxic effects of Co(II) complexes

Abstract 1-Benzothiazol-2-yl-3,5-dimethyl-1 H -pyrazole ( 1a ) and 1-benzothiazol-2-yl-5-(2-hydroxyphenyl)-3-methyl-1 H -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 IC 50 values in the range of 6.9–17.1 μM for three examined cell lines.