Isolation of potassium salt of oxadiazole-2-thione and in vitro anticancer activities of its Cu(II) and Zn(II) complexes against MDA-MB-231 human breast carcinoma cells.

A potassium 4-(pyridyl)-1,3,4-oxadiazole-2-thione was isolated in a basic medium, and its complexes [Cu(en)2(pot)2] (1) and [Zn(en)2(pot)2]HBr·CH3OH (2) containing ethylenediamine (en) as secondary ligand were synthesized and fully characterized. Upon changing the reaction conditions, the Cu(II) complex (1) adopts an octahedral geometry around the metal center. The cytotoxic activity of ligand (Kpot·H2O) along with complexes 1 and 2 was tested, and their anticancer activity against MDA-MB-231 human breast cancer cells was demonstrated, with complex 1 exhibiting superior cytotoxicity against these cells as compared to Kpot·H2O and complex 2. According to the DNA nicking assay, the ligand (Kpot·H2O) was found to be more potent to scavenge hydroxyl radicals even at a lower concentration (50 µg mL-1) than that of both complexes. The wound healing assay revealed that ligand Kpot·H2O and its complexes 1 and 2 attenuated the migration of the above-mentioned cell line. The loss of cellular and nuclear integrity and induction in the activity of Caspase-3 suggest the anticancer potential of ligand Kpot·H2O and its complexes 1 and 2 against MDA-MB-231 cells.

Nucleophilic versus Electrophilic Reactivity of Bioinspired Superoxido Nickel(II) Complexes.

The formation and detailed spectroscopic characterization of the first biuret-containing monoanionic superoxido-NiII intermediate [LNiO2 ]- as the Li salt [2; L=MeN[C(=O)NAr)2 ; Ar=2,6-iPr2 C6 H3 )] is reported. It results from oxidation of the corresponding [Li(thf)3 ]2 [LNiII Br2 ] complex M with excess H2 O2 in the presence of Et3 N. The [LNiO2 ]- core of 2 shows an unprecedented nucleophilic reactivity in the oxidative deformylation of aldehydes, in stark contrast to the electrophilic character of the previously reported neutral Nacnac-containing superoxido-NiII complex 1, [L'NiO2 ] (L'=CH(CMeNAr)2 ). According to density-functional theory (DFT) calculations, the remarkably different behaviour of 1 versus 2 can be attributed to their different charges and a two-state reactivity, in which a doublet ground state and a nearby spin-polarized doublet excited-state both contribute in 1 but not in 2. The unexpected nucleophilicity of the superoxido-NiII core of 2 suggests that such a reactivity may also play a role in catalytic cycles of Ni-containing oxygenases and oxidases.