Electronic energy transfer in dinuclear metal complexes containing meta-substituted phenylene units

The synthesis and photophysical properties of heterometallic dinuclear complexes based on ruthenium and osmium trisbipyridine units, Ru-mPh 3-Os and Ru-wPh5-Os, in which the metal complexes are linked via an oligophenylene bridge centrally connected in the meta position, are described. Electronic energy transfer from the excited ruthenium-based component (donor) to the osmium moiety (acceptor) has been investigated using steady-state and time-resolved spectroscopy. The results obtained for the meta-substituted compounds are compared with the analogous systems in which the phenylene spacers are substituted in the para position. The mechanism of energy transfer is discussed.