Five fluorescent ONO donor-based organotin(IV) complexes, [Sn IV (L 1−5 )Ph 2 ] (1−5), were synthesized by the onepot reaction method and fully characterized spectroscopically including the single-crystal X-ray diffraction studies of 2−4. Detailed photophysical characterization of all compounds was performed. All the compounds exhibited high luminescent properties with a quantum yield of 17−53%. Additionally, the results of cellular permeability analysis suggest that they are lipophilic and easily absorbed by cells. Confocal microscopy was used to examine the live cell imaging capability of 1−5, and the results show that the compounds are mostly internalized in mitochondria and exhibit negligible cytotoxicity at imaging concentration. Also, 1−5 exhibited high photostability as compared to the commercial dye and can be used in long-term real-time tracking of cell organelles. Also, it is found that the probes (1−5) are highly tolerable during the changes in mitochondrial morphology. Thus, this kind of low-toxic organotin-based fluorescent probe can assist in imaging of mitochondria within living cells and tracking changes in their morphology.

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The reaction of the Ru(PPh 3 ) 3 Cl 2 with HL 1À 3 À OH (À OH stands for the oxime hydroxyl group; HL 1 À OH = diacetylmonoxime-S-benzyldithiocarbazonate; HL 2 À OH = diacetylmonoxime-S-(4-methyl)benzyldithiocarbazonate; andgives three new ruthenium complexes [Ru II (L 1À 3 À H)(PPh 3 ) 2 Cl] (1-3) (À H stands for imine hydrogen) coordinated with dithiocarbazate imine as the final products. All ruthenium(II) complexes (1-3) have been characterized by elemental (CHNS) analyses, IR, UV-vis, NMR ( 1 H, 13 C, and 31 P) spectroscopy, HR-ESI-MS spectrometry and also, the structure of 1-2 was further confirmed by single crystal X-ray crystallography. The solution/aqueous stability, hydrophobicity, DNA interactions, and cell viability studies of 1-3 against HeLa, HT-29, and NIH-3T3 cell lines were performed. Cell viability results suggested 3 being the most cytotoxic of the series with IC 50 6.9 � 0.2 μM against HeLa cells. Further, an apoptotic mechanism of cell death was confirmed by cell cycle analysis and Annexin V-FITC/PI double staining techniques. In this regard, the live cell confocal microscopy results revealed that compounds primarily target the mitochondria against HeLa, and HT-29 cell lines. Moreover, these ruthenium complexes elevate the ROS level by inducing mitochondria targeting apoptotic cell death.

The transport and cytotoxicity of molybdenum-based drugs have been explained with the concept of chemical transformation, a very important idea in inorganic medicinal chemistry that is often overlooked in the interpretation of the biological activity of metal-containing systems. Two monomeric, [MoO2(L1)­(MeOH)] (1) and [MoO2(L2)­(EtOH)] (2), and two mixed-ligand dimeric MoVIO2 species, [{MoO2(L1–2)}2(μ-4,4′-bipy)] (3–4), were synthesized and characterized. The structures of the solid complexes were solved through SC-XRD, while their transformation in water was clarified by UV–vis, ESI-MS, and DFT. In aqueous solution, 1–4 lead to the penta-coordinated [MoO2(L1–2)] active species after the release of the solvent molecule (1 and 2) or removal of the 4,4′-bipy bridge (3 and 4). [MoO2(L1–2)] are stable in solution and react with neither serum bioligand nor cellular reductants. The binding affinity of 1–4 toward HSA and DNA were evaluated through analytical and computational methods and in both cases a non-covalent interaction is expected. Furthermore, the in vitro cytotoxicity of the complexes was also determined and flow cytometry analysis showed the apoptotic death of the cancer cells. Interestingly, μ-4,4′-bipy bridged complexes 3 and 4 were found to be more active than monomeric 1 and 2, due to the mixture of species generated, that is [MoO2(L1–2)] and the cytotoxic 4,4′-bipy released after their dissociation. Since in the cytosol neither the reduction of MoVI to MoV/IV takes place nor the production of reactive oxygen species (ROS) through Fenton-like reactions of 1–4 with H2O2 occurs, the mechanism of cytotoxicity should be attributable to the direct interaction with DNA that happens with a minor-groove binding which results in cell death through an apoptotic mechanism.

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