The condensation of 3-methoxy-2-hydroxybenzaldehyde and the diamines 1,2-diphenylendiamine, 1,2-diamine-2-methylpropane and 1,3-propanediamine yielded the dianionic tetradentate Schiff base ligands N,N -bis(2-hydroxy-4-methoxybenzylidene3 ) respectively. The organic compounds H 2 L 1 and H 2 L 2 have been characterized by elemental analysis, IR, 1 H and 13 C NMR spectroscopies and mass spectrometry electrospray (ES). The crystal structure of H 2 L 2 in solid state, solved by X-ray crystallography, is highly conditioned in the solid state by two N-H•••N intramolecular interactions. The synthesis of three new manganese(III) complexes 1-3, incorporating these ligands, H 2 L 1 -H 2 L 3 , and dicyanamide (DCA), is reported. The complexes 1-3 have been physicochemically characterized by elemental analysis, IR and paramagnetic 1 H NMR spectroscopy, ESI mass spectrometry, magnetic moment at room temperature and conductivity measurements. Complex 1 has been crystallographically characterized. The X-ray structure shows the self-assembly of the Mn(III)-Schiff base-DCA complex through -aquo bridges between neighbouring axial water molecules and also by -stacking interactions, establishing a dimeric structure. The manganese complexes were also tested as peroxidase mimics for the H 2 O 2 -mediated reaction with the water-soluble trap ABTS, showing complexes 1-2 relevant peroxidase activity in contrast with 3. The rhombicity around the metal ion can explain this catalytic behaviour.
A dinuclear Pb(ii) mesocate has been prepared with an unprecedented four-coordinated kernel in which the Pb(ii) lone pair is stereochemically active. This is the first time that this effect has been observed in a supramolecular Pb(ii) helicate or meso-helicate.
The design of artificial helicoidal molecules derived from metal ions with biological properties is one of the objectives within metallosupramolecular chemistry. Herein, we report three zinc helicates derived from a family of bisthiosemicarbazone ligands with different terminal groups, Zn2(LMe)2∙2H2O 1, Zn2(LPh)2∙2H2O 2 and Zn2(LPhNO2)23, obtained by an electrochemical methodology. These helicates have been fully characterized by different techniques, including X-ray diffraction. Biological studies of the zinc(II) helicates such as toxicity assays with erythrocytes and interaction studies with proteins and oligonucleotides were performed, demonstrating in all cases low toxicity and an absence of covalent interaction with the proteins and oligonucleotides. The in vitro cytotoxicity of the helicates was tested against MCF-7 (human breast carcinoma), A2780 (human ovarian carcinoma cells), NCI-H460 (human lung carcinoma cells) and MRC-5 (normal human lung fibroblasts), comparing the IC50 values with cisplatin. We will try to demonstrate if the terminal substituent of the ligand precursor exerts any effect in toxicity or in the antitumor activity of the zinc helicates.
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