RIGID RODLIKE DINUCLEAR RU OS COMPLEXES OF A NOVEL BRIDGING LIGAND - INTERCOMPONENT ENERGY AND ELECTRON-TRANSFER PROCESSES/

The PF6- sails of the dinuclear complexes [(bpy)(2)Ru(PAP)Ru(bpy)(2)]( 4+) (Ru(II)PAPRu(II)), [(bpy)(2)Os(PAP)Os (bpy)(2)](4+) (Os(II)PAPOs(I I)), and [(bpy)(2)Ru(PAP)Os(bpy)(2)](4+) (Ru(II)PAPOs(II)) have been p repared, where bpy 2,2'-bipyridine and PAP is a rodlike bridging ligan d made of an adamantane-based spacer collinear with the coordination a xis of two 1,10-phenanthroline units. In the prepared complexes, the m etal-metal distance is 2.1 nm. In the Ru(II)PAPOs(II) compound, photoi nduced energy transfer from the Ru-II-based to the Os-II-based unit ta kes place with rate constant 5.2 x 10(7) s(-1) at room temperature and 2.4 x 10(7) s(-1) al 77 K. In the mixed-valence Ru(II)PAPOs(III) comp ound, the luminescent excited stale of the Ru-II-based unit is quenche d via electron transfer by the Os-III-based unit with rate constant 7. 2 x 10(6) s(-1). The rate constant fur the back-electron-transfer reac tion is 8.3 x 10(3) s(-1).