Vectorial transfer of electronic energy in rod-like ruthenium-osmium dinuclear complexes

Dinuclear complexes containing ruthenium and osmium-based bis-terpyridyl chromophoric termini are prepared and their luminescence properties investigated. The two chromophoric units are connected by 1,4-phenylenes only, or phenylene and bicyclooctane spacers. In this way complete control of the geometry of the dinuclear complexes is achieved and these rigid species resemble molecular rods or girders featuring intermetal distances in the range 11-24 Angstrom. The Ru --> Os transfer of electronic excitation is energetically allowed and we have studied the effect on this process both of the intermetal separation and the electronic properties of the spacers, The main conclusions are that the phenylene spacers are very efficient in transmitting the intermetal electronic communication but an important role is also played by the spatial localization of the metal-to-ligand charge-transfer excited states involved in the excitation-transfer process.