Cobalt(III)-pyen systems as potential carriers of β-ketoester-based ligands.

Two cobalt(III) complexes containing different β-ketoesters, namely [Co(L1)(pyen)](ClO)·HO (1) and [Co(L2)(pyen)](ClO) (2) (pyen = N,N'-bis(pyridin-2-ylmethyl)ethylenediamine; L1 = methylacetoacetate; L2 = ethyl 4-chloroacetoacetate) have been prepared and investigated as prototypes of bioreductive prodrugs. The presence of β-ketoester and pyen ligands in 1 and 2, as well as the perchlorate counterions, was supported by IR spectroscopy and CHN elemental analysis. The composition molecular structure of both complexes was confirmed by NMR spectroscopy and ESI mass spectrometry.

DNA-interacting properties of two analogous square-planar cis-chlorido complexes: copper versus palladium.

Two square-planar coordination compounds, namely [Cu(CPYA)Cl] (1) and [Pd(CPYA)Cl] (2), were prepared from the ligand 4-chloro-N-(pyridin-2-ylmethyl)aniline (CPYA) and two chloride salts, and were fully characterized, including by X-ray diffraction. Spectroscopic, electrophoretic and AFM studies revealed that the two isostructural compounds were interacting differently with DNA. In both cases, the initial interaction involves electrostatic contacts of the CPYA ligand in the minor groove (as suggested by molecular docking), but subsequent strong binding occurs with the palladium(II) complex 2, whereas the binding with the copper complex 1 is weaker and concentration dependent.

Evaluation of the metal-dependent cytotoxic behaviour of coordination compounds.

The [Cu(L)Cl2]2 and [Pt(L)Cl2] complexes were prepared from the simple Schiff-base ligand (E)-phenyl-N-((pyridin-2-yl)methylene)methanamine (L) and respectively, CuCl2 and cis-[PtCl2(DMSO)2]. DNA-interaction studies revealed that the copper complex most likely acts as a DNA cleaver whereas the platinum complex binds to the double helix. Remarkably, cell-viability experiments with HeLa, MCF7 and PC3 cells showed that [Cu(L)Cl2]2 is an efficient cytotoxic agent whereas [Pt(L)Cl2] is not toxic, illustrating the crucial role played by the nature of the metal ion in the corresponding biological activity.

pH-Driven preparation of two related platinum(ii) complexes exhibiting distinct cytotoxic properties.

Reaction of cis-[PtCl(DMSO)] with the ligand 4-methyl-2-N-(2-pyridylmethylene)aminophenol (Hpyrimol, LH) in methanol at room temperature produces the complexes [PtCl2LH] or [PtClL], under acidic or basic conditions, respectively. The two platinum compounds exhibit distinct DNA-interacting properties, [PtCl2LH] showing a higher affinity for the biomolecules. Furthermore, [PtClL] is clearly more cytotoxic than [PtCl2LH] in three different cancer cell lines.