The EPR of NO. can be detected in the liquid and solid states when crystal fields are sufficient to remove the axial symmetry and separate the (pi*)x and (pi*)y orbitals by a few hundred reciprocal centimeters. The theory of the EPR spin Hamiltonian of bound NO. is reviewed, further developed, and then applied to the observed frozen-liquid spectra of NO. bound to Ru(II) obtained from RuIINO+ complexes by reduction. Comparisons to earlier reports on the observation of the EPR spectra of NO. are made.

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A new calix [4]arene receptor modiÐed with 8-hydroxyquinoline has been synthesised, exhibiting luminescence and energy transfer properties in the presence of coordinated Eu3' and Tb3' ions.

Redox properties of copper complexes are important for their catalytic functions in vitro and in biological systems, and can contribute to their reactivity toward selected targets. In order to evaluate the influence of different ligands on the reactivity of copper ions, comparative studies were carried out with some copper(II) complexes containing a tridentate imine, or a tetradentate di-Schiff base ligand with a mixed pyridine, pyrazine, or imidazole donor set, acting as catalysts in the oxidation of 2-deoxy-D-ribose. Addition of the reducing agent glutathione (gamma-glutamylcysteinylglycine; GSH), which can also act as a good ligand for copper(I), mediated the oxidation of the substrate. For some of these compounds, a reductive activation followed by competition for the metal ion was verified, with formation of copper(I)-glutathione complex monitored by fluorescence measurements. For others, however, the reduction of the metal by the glutathione seems to not occur. In the presence of hydrogen peroxide, the oxidative damage is significantly enhanced for all the complexes tested. Redox potential measurements by cyclic voltammetry corroborated partially these results, indicating that the most reactive complexes are those with more positive redox potential. Evidence for site-specific attack to 2-deoxy-D-ribose was also observed, consistent with the intermediary formation of a copper-hydroxyl species, [LCu(II)(*OH)], rather than 'free' hydroxyl radical.