NEAR-INFRARED LUMINESCENCE OF SUPRAMOLECULAR SPECIES CONSISTING OF OSMIUM(II)-POLYPYRIDINE AND OR RUTHENIUM(II)-POLYPYRIDINE COMPONENTS

The luminescence behavior of 10 homometallic (Os2+) and heterometallic (Os2+/Ru2+) polynuclear metal complexes containing 2,3-dpp and/or 2,5 -dpp as bridging ligands and bpy and/or biq as terminal ligands has be en investigated (dpp = bis(2-pyridyl)pyrazine; bpy = 2,2'-bipyridine; biq = 2,2'-biquinoline). The nuclearity of the investigated compounds varies from 2 to 10. Each compound may be considered as a supramolecul ar species constituted by an assembly of distinct mononuclear componen ts. All the examined compounds exhibit a luminescence band in the 850- 1000-nm spectral region (rigid matrix, 90 K), which can be assigned to ''triplet'' metal-to-ligand charge-transfer levels localized on Os-co ntaining components. Correlations among energies of the emission bands , oxidation potentials, compositions of the metal-based components, an d their positions in the supramolecular array allow an unequivocal ide ntification of the components responsible for the observed luminescenc e. For the Ru2+/Os2+ mixed-metal compounds, only an Os-based luminesce nce is observed. Exoergonic electronic energy transfer along a row of components arranged in an 'energy cascade' pattern is 100% efficient. The results obtained elucidate the role played by intercomponent energ y transfer in polynuclear metal complexes and may help in designing su pramolecular structures where the pattern of energy migration is synth etically controlled.