Anna Adach

New oxovanadium(IV) complexes with pincer ligand obtained in situ: experimental and theoretical studies on the structure, spectroscopic properties and antitumour activity

Experimental and theoretical studies on the structure and spectroscopic properties of two complexes: [VOL1(NCS)2] (1) and [VOL1(NCS)2]·C6H5CH3 (2) where L1-N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)amine have been reported. The products, isolated in a one-pot synthesis, contain a multipodal pincer ligand L1 obtained in situ from the system containing 1-hydroxymethyl-3,5-dimethylpyrazole (L) as one of the substrates. The crystal structure, electronic (UV-VIS) and infrared (IR) spectra of the complexes have been analyzed. The combined use of experiments and computations allowed a firm assignment of the majority of the observed electronic and vibrational transitions. Theoretical (DFT) calculations have been carried out at the B3LYP/LanL2DZ level to investigate the geometry of 1 and 2. They were found to be in a good agreement with the experimental results. Additionally the biological activity of complex 2 was investigated. Complex 2 exhibited anti-proliferative activity towards a panel of human cancer cells (hepatocellular carcinoma Hep G2, lung carcinoma A549, colorectal adenocarcinomas SW 480 and SW 620). The anti-proliferative potency of complex 2 and its higher selectivity towards cancer cells than those of the vanadium salt tested, makes it an interesting candidate for further investigation of its anti-cancer properties.

Systematic coordination chemistry and cytotoxicity of copper(II) complexes with methyl substituted 4-nitropyridine N-oxides.

Three new nitrato copper(II) complexes of dimethyl substituted 4-nitropyridine N-oxide were synthesized and characterized by elemental analysis, magnetic, spectroscopic, thermal and X-ray methods, respectively. They were isolated as trans isomers, mononuclear (μ=1.70-1.88 BM), five (1-2) and four (3) coordinate species of general formula [Cu(NO3)2(H2O)L2] where L=2,3-dimethyl-, 2,5-dimethyl-4-nitropyridine N-oxide and [Cu (NO3)2L2], L=3,5-dimethyl-4-nitropyridine N-oxide, respectively. The X-ray crystal structure of (1) (L=2,3-dimethyl-4-nitropyridine N-oxide) was determined. The organic ligands, the complexes and copper hexaqua ion as a reference were tested in vitro on the cytotoxic activity against human cancer cell lines: MCF-7 (breast), SW-707 (colon) and P-388 (murine leukemia). The complexes are relatively strong cytotoxic agents towards P-388 cell line. Comparative analysis was performed for all known copper(II) complexes containing methyl derivatives of the 4-nitropyridine N-oxide on the basis of their composition, structure and cytotoxic activities. To obtain the typical structure for these species (i.e., 4-coordinate mononuclear of the type trans-[Cu(inorganic anion)2L2]), two methyl groups must be situated on both sides of nitrogen atom(s) (i.e., NO and NO2) in the ligand. The biological activity was found to be strongly dependent upon the number of the methyl groups and the type of cell line. The best cytotoxic results were found for the complexes without substituents or with one methyl group. Generally, for all cell lines, the complexation increased cytotoxicity when compared with the free ligands.

A family of complexes with N-scorpionate-type and other N-donor ligands obtained in situ from pyrazole derivative and zerovalent cobalt. Physicochemical and cytotoxicity studies

In situ syntheses and X-ray structures of three novel cationic–anionic complexes: [CoL1Br][ZnL2L3ZnBr5] (1), and [CoL1Cl][ZnL3Br3] (2) and [CoL1Cl][ZnL3Cl3] (3) L1 = N,N,N-tris(3,5-dimethylpyrazol-1-ylmethyl)amine, L2 = hexamethylenetetramine (urotropine), L3 = 3,5-dimethylpyrazole, have been reported. The presence of three different organic ligands (L1, L2 and L3) in isolated complexes results from various reactions taking place in the system which contains zerovalent cobalt and 1-hydroxymethyl-3,5-dimethylpyrazole as starting materials, in the presence of Zn(II) ions. The scorpionate-type ligand (L1) formed in situ, possesses four potential donor sites, specifically three nitrogen donor atoms from the pyrazole rings, and one from tertiary amine, all of which coordinate to Co(II). They form a distorted trigonal bipyramidal [CoL1X]+ cation whereas anionic parts include tetrahedrally coordinated zinc(II). The crystal structures and electronic (UV-Vis), infrared (FT-IR) spectra and thermal investigation of the isolated complexes have been analysed and discussed. Finally, the biological activity of 1–3 complexes was assessed. All the tested complexes expressed higher selectivity towards human cancer cells than towards human normal cells and showed a substantial antitumor activity against: colorectal adenocarcinomas Caco-2 and SW 620, hepatocellular carcinoma Hep G2 and lung carcinoma A549.