Abstract: Metal complexes of 1,4-dihydroxy-benzoquinone and its homologues (H2C6X2O4) are reviewed, focusing on assembled structures based on their X-ray crystallographic structures reported so far. A wide variety of crystal structures based on mononuclear, binuclear, polynuclear complexes and extended structures of coordination polymers or hydrogen bond linked networks are listed in relation to the coordination modes such as the monodentate, bidentate, and bis-bidentate form of the ligands. Their physico-chemical properties such as redox, UV-vis, EPR and magnetic properties are described. The ligand, H2C6X2O4, discussed here is one of the most useful multifunctional ligands, affording not only various self-assembled frameworks via coordination, hydrogen, and coulomb linkages, but also unique electronic structures, which are accompanied by charged and spin states. Their characteristics are mentioned in detail. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract: 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.

Abstract: The coordinating ability of aromatic diamines is conditioned both by the low basicity of the nitrogen atoms and their situation in ortho, meta or para positions on the aromatic ring. Important aspects of the aromatic diamines taking into account their possible applications are: processes based on electron transfer forming Wurster type radical colored cations; trace analysis of metal ions and other species based on catalysis of the oxidative coloration system; the development of biosensors coated with poly(o-phenylenediamine) and their mutagenic and toxic character. o-Phenylenediamine ligands coordinate in a monodentate, chelating bidentate and bridging bidentate fashion in dinuclear complexes; p-phenylenediamine is mainly a bridging bidentate ligand as expected.