Syntheses, Structures, and Bioactivity Evaluation of some Transition Metal Complexes with Aroylbis(N,N‐diethylthioureas) Derived from Natural Compounds

Abstract

Two novel benzoylthioureas derived from gallic acid, (tri-Oacetyl)galloyl-N,N-diethylthiourea HL 1 , and cinnamic acid, cinnamoyl-N,N-diethylthiourea HL 2 have been successfully prepared and characterized by means of elemental analysis, IR, NMR, high-resolution MS, and X-ray crystallography. The organic ligands react with Ni(AcO) 2 and Cu(AcO) 2 in MeOH under formation of bis-complexes with the compositions of [M(L) 2 ] (M=Ni 2 + , Cu 2 + ; L=L 1 , L 2 ). Similar reactions with Co(AcO) 2 , however, result in Co(III) tris-complexes [Co(L) 3 ] (L=L 1 , L 2 ) with the metal ions oxidized presumably by atmospheric dioxygen. X-ray crystallography and spectroscopic characterization reveal a cis square-planar coordination in the bis-complexes and facial octahedral geometry in the tris-complexes. In all of metal complexes, the deprotonated organic compounds ({L 1 } À and {L 2 } À ) serve as (S,O)-bidentate ligands. The ligand HL 1 and its Ni(II) and Cu(II) complexes exhibit weak antiproliferative effects on the human MCF7 breast and HepG2 liver cancer cells with IC 50 values in the range of 60-115 μM. Surprisingly, the triscomplex [Co(L 1 ) 3 ] exhibits high cytotoxicity with IC 50 values of 22.23 � 1.58 μM for MCF7 and 28.30 � 3.09 μM for HepG2 cancer cells. The activity against MCF7 cells is even more than that of cisplatin under the same conditions.