The cis/trans isomerization of Cu(II)-bis-(glycinato) complex in solution: a computer aided multifrequency EPR and DFT/PCM calculation study.

In this paper the Cu(II)-bis-(glycinato) complex has been analysed in solution by applying a combined approach of multifrequency EPR and DFT/PCM calculations. The accuracy in the determination of magnetic parameters has been reached by the use of a unique simulation program (COSMOS) for the whole range of temperatures analysed and by the error analysis. A change in magnetic parameters was envisaged in the 243-253 K range of temperature, and was interpreted in terms of stabilization, near the freezing point of the solution, of one of the isomers of the complex. A DFT/PCM computational model was crucial in assigning, on the basis of the experimental superhyperfine interaction value, the isomer to the trans form.

EPR characterization of mono(thiosemicarbazones) copper(II) complexes. Note II.

Copper(II) complexes with thiosemicarbazones have been shown to be more active in cell destruction, in the inhibition of DNA synthesis than the uncomplexed ligand. Several derivatives of thiosemicarbazones and their iron and copper complexes have been studied for their cytotoxicity and inhibiting activity against DNA synthesis. In the present work complexes formed in H2O-DMSO solution between copper(II) and the acetophenone thiosemicarbazone (ATSC) and the o-aminobenzaldehyde thiosemicarbazone (o-NH2TSC) have been studied. EPR studies have been performed at different pH values and metal-to-ligand ratios. The spectra have been recorded at both room (298 K) and low temperatures (120 K). A possible relationship between structure and activity is attempted on the basis of the EPR data.

EPR and O2.- scavenger activity: Cu(II)-peptide complexes as superoxide dismutase models.

Several copper(II) complexes with aminoacids and peptides are known to show superoxide dismutase (SOD)-like activity. EPR spectroscopy has proved to be a useful tool for studying the complex equilibria of the copper(II) ion and various ligands of biological importance in solution. In the present work, a variety of copper(II) complexes with di-, tri- and tetra-peptides containing only glycine residues (GG, GGG and GGGG) and others containing a histidyl residue in different positions (HGG, GHG, GGH and GGHG) have been investigated. EPR parameters obtained by extensive use of computer simulation of spectra lead to reliable spin Hamiltonian EPR parameters at both room temperature and in frozen solution. The molecular orbital coefficients computed from the anisotropic EPR data and the d-d electronic energies are used to characterize different arrangements of the complexes. Estimation of the scavenger activity of the complexes due to the particular environment created by the ligands around copper is discussed in the frame of the structure-activity relationship.