Supramolecular assemblies of ruthenium complexes and porphyrins

The build-up of polymetallic supermolecules based on porphyrins and ruthenium bipyridine complexes has been pursued with great interest. A relevant series of symmetric polynuclear species has been obtained by attaching four [Ru-II(bipy)(2)Cl] groups to the pyridyl substituents of meso-tetra(4-pyridyl)porphyrin and its metallated derivatives. These compounds display a rich electrochemistry and versatile catalytic and photochemical properties, associated with the ruthenium-bipyridine and metalloporphyrin complexes. The supermolecular species interact very strongly with DNA, yielding by irradiation with visible light, very efficient single-strand breaks and formation of 8-oxo-7,8-dihydroxo-2'-deoxyguanosine. Another interesting property of the supramolecular porphyrins is their ability to form homogeneous and adherent molecular films by dip-coating. When combined with anionic porphyrins, self-assembled films can be generated, layer-by-layer, in a controlled way. Both types of films display photoaction response in the presence of visible light. The modified electrodes exhibit rectifying response in the presence of reducing species, demonstrating excellent performance as FIA detectors for biological and environmentally relevant substrates such as dopamine, NADH, ascorbic acid and sulfite ions. (C) 2000 Elsevier Science S.A. All rights reserved.