Hexanuclear polypyridine complexes containing different metals, bridging ligands and/or terminal ligands. Absorption spectra, electrochemical oxidation, luminescence properties and intercomponent energy transfer
✍ Scribed by Gianfranco Denti; Scolastica Serroni; Sebastiano Campagna; Vittorio Ricevuto; Alberto Juris; Mauro Ciano; Vincenzo Balzani
- Book ID
- 104138786
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 652 KB
- Volume
- 198-200
- Category
- Article
- ISSN
- 0020-1693
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✦ Synopsis
Four novel hexanuclear complexes of general formula [(L)zM(~-BL)]zM(~-BL)M[(p-BL)M(L)&rz+,
where the metal ions M are RI?' and/or OS", the bridging ligands BL are 2,3-dpp and/or 2,5-dpp, and the terminal ligands L are bpy and/or biq, have been investigated (dpp = bis(2-pyridyl)pyrazine; bpy = 2,2'-bipyridine; biq = 2,2'biquinohne).
These polymetallic complexes can be considered as supramolecular species made of six distinct metal-containing units. They display very intense ligand centered absorption bands in the UV region (E,,,, in the order of 2.5 X ld M-' cm-') and broad and intense bands in the visible region (E,, in the order of 5 X 104 M-' cm-'). On electrochemical oxidation, the metal centers are oxidized at the same or different potentials depending on the nature of the metal ions (Ru2+ or OS'+) and on their positions (inner or outer) in the supramolecular structure. For all the novel compounds, luminescence can be observed in the red or near-IR spectral region. The luminescence properties, which are characteristic of specitic metal-containing units, show that exoergonic electronic energy transfer between adjacent units is 100% efficient, whereas it is much lower when higher energy units are interposed. Various energy migration patterns can be obtained by placing different units in suitable sites of the supramolecular array.