Abstract“Alligator clips” suitable for grafting on H‐terminated silicon or gold surfaces have been incorporated into single‐molecule magnets (SMMs) of the Fe4 family. Tripodal ligands 2,2‐bis(hydroxymethyl)‐10‐undecen‐1‐ol (H3L1) and 11‐(acetylthio)‐2,2‐bis(hydroxymethyl)undecan‐1‐ol (H3L2) have been used to replace the six methoxide bridges in [Fe4(OMe)6(dpm)6], affording new Fe4 derivatives [Fe4(L1)2(dpm)6] (1) and [Fe4(L2)2(dpm)6] (2) in high yield (Hdpm = dipivaloylmethane). The molecular structures have been unambiguously established by XRD combined with ESI‐MS and magnetic characterization techniques, including DC and AC magnetometry and high‐frequency EPR spectroscopy. The two SMMs have an S = 5 ground state and an easy‐axis magnetic anisotropy leading to slow relaxation of the magnetization at low temperature, with effective anisotropy barriers of 15.9(2) K in 1 and 15.1(2) K in 2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The thioamido function of [CuCl2(1H)]Cl (2) (1=4-amino-1,4-dihydro-3-(2-pyridyl)-5-thioxo-1,2,4-triazole), a cytotoxic copper complex, was converted into thioether moieties, leading to the synthesis of [CuCl2(3)]2 (4) and [CuCl2(5)] (6) (3=6-methyl-3-pyridin-2-yl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine; 5=4-amino-5-ethylthio-3-(2-pyridyl)-1,2,4-triazole). These complexes were structurally characterized, and their stability constants, along with their biological activity, were determined. 4 and 6 were slightly less stable and significantly less active than 2. However, as 2, both complexes induced nonapoptotic vacuolar cell death. Copper uptake, investigated in both 2-sensitive and -insensitive cell types, was markedly higher in sensitive cells where it was associated with an increase in oxidized glutathione. These data suggest that the thioamido function enhances the cytotoxicity of copper complexes in cancer cells promoting the accumulation of the metal and its interaction with cell thiols.

Here, we report the antiproliferative/cytotoxic properties of 8-hydroxyquinoline (8-HQ) derivatives on HeLa cells in the presence of transition metal ions (Cu(2+), Fe(3+), Co(2+), Ni(2+)). Two series of ligands were tested, the arylvinylquinolinic L1-L8 and the arylethylenequinolinic L9-L16, which can all interact with metal ions by virtue of the N,O donor set of 8-HQ; however, only L9-L16 are flexible enough to bind the metal in a multidentate fashion, thus exploiting the additional donor functions. L1-L16 were tested for their cytotoxicity on HeLa cancer cells, both in the absence and in the presence of copper. Among them, the symmetric L14 exhibits the highest differential activity between the ligand alone (IC50 = 23.7 μM) and its copper complex (IC50 = 1.8 μM). This latter, besides causing a significant reduction of cell viability, is associated with a considerable accumulation of the metal inside the cells. Metal accumulation is also observed when the cells are incubated with L14 complexed with other late transition metal ions (Fe(3+), Co(2+), Ni(2+)), although the biological response of HeLa cells is different. In fact, while Ni/L14 and Co/L14 exert a cytostatic effect, both Cu/L14 and Fe/L14 trigger a caspase-independent paraptotic process, which results from the induction of a severe oxidative stress and the unfolded protein response.

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